diff --git a/backend/DramaLing.Api/Controllers/AIController.cs b/backend/DramaLing.Api/Controllers/AIController.cs
index f5870dd..b39d99b 100644
--- a/backend/DramaLing.Api/Controllers/AIController.cs
+++ b/backend/DramaLing.Api/Controllers/AIController.cs
@@ -7,6 +7,7 @@ using System.Diagnostics;
 namespace DramaLing.Api.Controllers;
 
 [Route("api/ai")]
+[AllowAnonymous]
 public class AIController : BaseController
 {
     private readonly IAnalysisService _analysisService;
@@ -24,7 +25,6 @@ public class AIController : BaseController
     /// <param name="request">分析請求</param>
     /// <returns>分析結果</returns>
     [HttpPost("analyze-sentence")]
-    [AllowAnonymous]
     public async Task<IActionResult> AnalyzeSentence(
         [FromBody] SentenceAnalysisRequest request)
     {
@@ -33,11 +33,7 @@ public class AIController : BaseController
 
         try
         {
-            // For testing without auth - use dummy user ID
-            var userId = "test-user-id";
-
-            _logger.LogInformation("Processing sentence analysis request {RequestId} for user {UserId}",
-                requestId, userId);
+            _logger.LogInformation("Processing sentence analysis request {RequestId}", requestId);
 
             // Input validation
             if (!ModelState.IsValid)
@@ -86,7 +82,6 @@ public class AIController : BaseController
     /// 健康檢查端點
     /// </summary>
     [HttpGet("health")]
-    [AllowAnonymous]
     public IActionResult GetHealth()
     {
         var healthData = new
@@ -104,7 +99,6 @@ public class AIController : BaseController
     /// 取得分析統計資訊
     /// </summary>
     [HttpGet("stats")]
-    [AllowAnonymous]
     public async Task<IActionResult> GetAnalysisStats()
     {
         try
diff --git a/backend/DramaLing.Api/Controllers/AnalysisController.cs b/backend/DramaLing.Api/Controllers/AnalysisController.cs
deleted file mode 100644
index e8d7b4f..0000000
--- a/backend/DramaLing.Api/Controllers/AnalysisController.cs
+++ /dev/null
@@ -1,124 +0,0 @@
-using Microsoft.AspNetCore.Mvc;
-using Microsoft.AspNetCore.Authorization;
-using DramaLing.Api.Models.DTOs;
-using DramaLing.Api.Services;
-using System.Diagnostics;
-
-namespace DramaLing.Api.Controllers;
-
-[Route("api/analysis")]
-[AllowAnonymous]
-public class AnalysisController : BaseController
-{
-    private readonly IAnalysisService _analysisService;
-
-    public AnalysisController(
-        IAnalysisService analysisService,
-        ILogger<AnalysisController> logger) : base(logger)
-    {
-        _analysisService = analysisService;
-    }
-
-    /// <summary>
-    /// 智能分析英文句子
-    /// </summary>
-    /// <param name="request">分析請求</param>
-    /// <returns>分析結果</returns>
-    [HttpPost("analyze")]
-    public async Task<IActionResult> AnalyzeSentence([FromBody] SentenceAnalysisRequest request)
-    {
-        var requestId = Guid.NewGuid().ToString();
-        var stopwatch = Stopwatch.StartNew();
-
-        try
-        {
-            // Input validation
-            if (!ModelState.IsValid)
-            {
-                return HandleModelStateErrors();
-            }
-
-            _logger.LogInformation("Processing sentence analysis request {RequestId}", requestId);
-
-            // 使用帶快取的分析服務
-            var options = request.Options ?? new AnalysisOptions();
-            var analysisData = await _analysisService.AnalyzeSentenceAsync(
-                request.InputText, options);
-
-            stopwatch.Stop();
-            analysisData.Metadata.ProcessingDate = DateTime.UtcNow;
-
-            _logger.LogInformation("Sentence analysis completed for request {RequestId} in {ElapsedMs}ms",
-                requestId, stopwatch.ElapsedMilliseconds);
-
-            var response = new SentenceAnalysisResponse
-            {
-                Success = true,
-                ProcessingTime = stopwatch.Elapsed.TotalSeconds,
-                Data = analysisData
-            };
-
-            return SuccessResponse(response);
-        }
-        catch (ArgumentException ex)
-        {
-            _logger.LogWarning(ex, "Invalid input for request {RequestId}", requestId);
-            return ErrorResponse("INVALID_INPUT", ex.Message, null, 400);
-        }
-        catch (InvalidOperationException ex)
-        {
-            _logger.LogError(ex, "AI service error for request {RequestId}", requestId);
-            return ErrorResponse("AI_SERVICE_ERROR", "AI服務暫時不可用", null, 500);
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError(ex, "Unexpected error processing request {RequestId}", requestId);
-            return ErrorResponse("INTERNAL_ERROR", "伺服器內部錯誤", null, 500);
-        }
-    }
-
-    /// <summary>
-    /// 健康檢查端點
-    /// </summary>
-    [HttpGet("health")]
-    public IActionResult GetHealth()
-    {
-        var healthData = new
-        {
-            Status = "Healthy",
-            Service = "Analysis Service",
-            Timestamp = DateTime.UtcNow,
-            Version = "1.0"
-        };
-
-        return SuccessResponse(healthData);
-    }
-
-    /// <summary>
-    /// 取得分析統計資訊
-    /// </summary>
-    [HttpGet("stats")]
-    public async Task<IActionResult> GetAnalysisStats()
-    {
-        try
-        {
-            var stats = await _analysisService.GetAnalysisStatsAsync();
-            var statsData = new
-            {
-                TotalAnalyses = stats.TotalAnalyses,
-                CachedAnalyses = stats.CachedAnalyses,
-                CacheHitRate = stats.CacheHitRate,
-                AverageResponseTimeMs = stats.AverageResponseTimeMs,
-                LastAnalysisAt = stats.LastAnalysisAt,
-                ProviderUsage = stats.ProviderUsageStats
-            };
-
-            return SuccessResponse(statsData);
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError(ex, "Error getting analysis stats");
-            return ErrorResponse("INTERNAL_ERROR", "無法取得統計資訊");
-        }
-    }
-}
\ No newline at end of file
diff --git a/backend/DramaLing.Api/Controllers/AudioController.cs b/backend/DramaLing.Api/Controllers/AudioController.cs
deleted file mode 100644
index 132733e..0000000
--- a/backend/DramaLing.Api/Controllers/AudioController.cs
+++ /dev/null
@@ -1,218 +0,0 @@
-using Microsoft.AspNetCore.Mvc;
-using Microsoft.AspNetCore.Authorization;
-using DramaLing.Api.Models.Dtos;
-using DramaLing.Api.Services;
-
-namespace DramaLing.Api.Controllers;
-
-[Route("api/[controller]")]
-[Authorize]
-public class AudioController : BaseController
-{
-    private readonly IAudioCacheService _audioCacheService;
-    private readonly IAzureSpeechService _speechService;
-
-    public AudioController(
-        IAudioCacheService audioCacheService,
-        IAzureSpeechService speechService,
-        ILogger<AudioController> logger) : base(logger)
-    {
-        _audioCacheService = audioCacheService;
-        _speechService = speechService;
-    }
-
-    /// <summary>
-    /// Generate audio from text using TTS
-    /// </summary>
-    /// <param name="request">TTS request parameters</param>
-    /// <returns>Audio URL and metadata</returns>
-    [HttpPost("tts")]
-    public async Task<IActionResult> GenerateAudio([FromBody] TTSRequest request)
-    {
-        try
-        {
-            if (string.IsNullOrWhiteSpace(request.Text))
-            {
-                return BadRequest(new TTSResponse
-                {
-                    Error = "Text is required"
-                });
-            }
-
-            if (request.Text.Length > 1000)
-            {
-                return BadRequest(new TTSResponse
-                {
-                    Error = "Text is too long (max 1000 characters)"
-                });
-            }
-
-            if (!IsValidAccent(request.Accent))
-            {
-                return BadRequest(new TTSResponse
-                {
-                    Error = "Invalid accent. Use 'us' or 'uk'"
-                });
-            }
-
-            if (request.Speed < 0.5f || request.Speed > 2.0f)
-            {
-                return BadRequest(new TTSResponse
-                {
-                    Error = "Speed must be between 0.5 and 2.0"
-                });
-            }
-
-            var response = await _audioCacheService.GetOrCreateAudioAsync(request);
-
-            if (!string.IsNullOrEmpty(response.Error))
-            {
-                return ErrorResponse("TTS_ERROR", response.Error, null, 500);
-            }
-
-            return SuccessResponse(response);
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError(ex, "Error generating audio for text: {Text}", request.Text);
-            return StatusCode(500, new TTSResponse
-            {
-                Error = "Internal server error"
-            });
-        }
-    }
-
-    /// <summary>
-    /// Get cached audio by hash
-    /// </summary>
-    /// <param name="hash">Audio cache hash</param>
-    /// <returns>Cached audio URL</returns>
-    [HttpGet("tts/cache/{hash}")]
-    public async Task<ActionResult<TTSResponse>> GetCachedAudio(string hash)
-    {
-        try
-        {
-            // 實現快取查詢邏輯
-            // 這裡應該從資料庫查詢快取的音頻
-            return NotFound(new TTSResponse
-            {
-                Error = "Audio not found in cache"
-            });
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError(ex, "Error retrieving cached audio: {Hash}", hash);
-            return StatusCode(500, new TTSResponse
-            {
-                Error = "Internal server error"
-            });
-        }
-    }
-
-    /// <summary>
-    /// Evaluate pronunciation from uploaded audio
-    /// </summary>
-    /// <param name="audioFile">Audio file</param>
-    /// <param name="targetText">Target text for pronunciation</param>
-    /// <param name="userLevel">User's CEFR level</param>
-    /// <returns>Pronunciation assessment results</returns>
-    [HttpPost("pronunciation/evaluate")]
-    public async Task<ActionResult<PronunciationResponse>> EvaluatePronunciation(
-        IFormFile audioFile,
-        [FromForm] string targetText,
-        [FromForm] string userLevel = "B1")
-    {
-        try
-        {
-            if (audioFile == null || audioFile.Length == 0)
-            {
-                return BadRequest(new PronunciationResponse
-                {
-                    Error = "Audio file is required"
-                });
-            }
-
-            if (string.IsNullOrWhiteSpace(targetText))
-            {
-                return BadRequest(new PronunciationResponse
-                {
-                    Error = "Target text is required"
-                });
-            }
-
-            // 檢查檔案大小 (最大 10MB)
-            if (audioFile.Length > 10 * 1024 * 1024)
-            {
-                return BadRequest(new PronunciationResponse
-                {
-                    Error = "Audio file is too large (max 10MB)"
-                });
-            }
-
-            // 檢查檔案類型
-            var allowedTypes = new[] { "audio/wav", "audio/mp3", "audio/mpeg", "audio/ogg" };
-            if (!allowedTypes.Contains(audioFile.ContentType))
-            {
-                return BadRequest(new PronunciationResponse
-                {
-                    Error = "Invalid audio format. Use WAV, MP3, or OGG"
-                });
-            }
-
-            using var audioStream = audioFile.OpenReadStream();
-            var request = new PronunciationRequest
-            {
-                TargetText = targetText,
-                UserLevel = userLevel
-            };
-
-            var response = await _speechService.EvaluatePronunciationAsync(audioStream, request);
-
-            if (!string.IsNullOrEmpty(response.Error))
-            {
-                return StatusCode(500, response);
-            }
-
-            return Ok(response);
-        }
-        catch (Exception ex)
-        {
-            _logger.LogError(ex, "Error evaluating pronunciation for text: {Text}", targetText);
-            return StatusCode(500, new PronunciationResponse
-            {
-                Error = "Internal server error"
-            });
-        }
-    }
-
-    /// <summary>
-    /// Get supported voices for TTS
-    /// </summary>
-    /// <returns>List of available voices</returns>
-    [HttpGet("voices")]
-    public ActionResult<object> GetVoices()
-    {
-        var voices = new
-        {
-            US = new[]
-            {
-                new { Id = "en-US-AriaNeural", Name = "Aria", Gender = "Female" },
-                new { Id = "en-US-GuyNeural", Name = "Guy", Gender = "Male" },
-                new { Id = "en-US-JennyNeural", Name = "Jenny", Gender = "Female" }
-            },
-            UK = new[]
-            {
-                new { Id = "en-GB-SoniaNeural", Name = "Sonia", Gender = "Female" },
-                new { Id = "en-GB-RyanNeural", Name = "Ryan", Gender = "Male" },
-                new { Id = "en-GB-LibbyNeural", Name = "Libby", Gender = "Female" }
-            }
-        };
-
-        return Ok(voices);
-    }
-
-    private static bool IsValidAccent(string accent)
-    {
-        return accent?.ToLower() is "us" or "uk";
-    }
-}
\ No newline at end of file
diff --git a/backend/DramaLing.Api/Controllers/FlashcardsController.cs b/backend/DramaLing.Api/Controllers/FlashcardsController.cs
index d1f8841..97bb6a1 100644
--- a/backend/DramaLing.Api/Controllers/FlashcardsController.cs
+++ b/backend/DramaLing.Api/Controllers/FlashcardsController.cs
@@ -2,6 +2,7 @@ using Microsoft.AspNetCore.Mvc;
 using DramaLing.Api.Models.Entities;
 using DramaLing.Api.Repositories;
 using Microsoft.AspNetCore.Authorization;
+using DramaLing.Api.Utils;
 
 namespace DramaLing.Api.Controllers;
 
@@ -41,7 +42,8 @@ public class FlashcardsController : BaseController
                     f.Example,
                     f.ExampleTranslation,
                     f.IsFavorite,
-                    f.DifficultyLevel,
+                    DifficultyLevelNumeric = f.DifficultyLevelNumeric,
+                    CEFR = CEFRHelper.ToString(f.DifficultyLevelNumeric),
                     f.CreatedAt,
                     f.UpdatedAt
                 }),
@@ -84,12 +86,13 @@ public class FlashcardsController : BaseController
                 Pronunciation = request.Pronunciation,
                 Example = request.Example,
                 ExampleTranslation = request.ExampleTranslation,
-                DifficultyLevel = "A2", // 預設等級
+                DifficultyLevelNumeric = CEFRHelper.ToNumeric(request.CEFR ?? "A0"),
                 CreatedAt = DateTime.UtcNow,
                 UpdatedAt = DateTime.UtcNow
             };
 
             await _flashcardRepository.AddAsync(flashcard);
+            await _flashcardRepository.SaveChangesAsync();
 
             return SuccessResponse(flashcard, "詞卡創建成功");
         }
@@ -161,6 +164,7 @@ public class FlashcardsController : BaseController
             flashcard.UpdatedAt = DateTime.UtcNow;
 
             await _flashcardRepository.UpdateAsync(flashcard);
+            await _flashcardRepository.SaveChangesAsync();
 
             return SuccessResponse(flashcard, "詞卡更新成功");
         }
@@ -190,6 +194,7 @@ public class FlashcardsController : BaseController
             }
 
             await _flashcardRepository.DeleteAsync(flashcard);
+            await _flashcardRepository.SaveChangesAsync();
 
             return SuccessResponse(new { Id = id }, "詞卡已刪除");
         }
@@ -222,6 +227,7 @@ public class FlashcardsController : BaseController
             flashcard.UpdatedAt = DateTime.UtcNow;
 
             await _flashcardRepository.UpdateAsync(flashcard);
+            await _flashcardRepository.SaveChangesAsync();
 
             var result = new {
                 Id = flashcard.Id,
@@ -253,4 +259,5 @@ public class CreateFlashcardRequest
     public string Pronunciation { get; set; } = string.Empty;
     public string Example { get; set; } = string.Empty;
     public string? ExampleTranslation { get; set; }
+    public string? CEFR { get; set; } = string.Empty;
 }
\ No newline at end of file
diff --git a/backend/DramaLing.Api/Controllers/ImageGenerationController.cs b/backend/DramaLing.Api/Controllers/ImageGenerationController.cs
index 81f0aa2..3eb65ef 100644
--- a/backend/DramaLing.Api/Controllers/ImageGenerationController.cs
+++ b/backend/DramaLing.Api/Controllers/ImageGenerationController.cs
@@ -157,7 +157,7 @@ public class ImageGenerationController : BaseController
     private Guid GetCurrentUserId()
     {
         // 暫時使用固定測試用戶 ID，與 FlashcardsController 保持一致
-        return Guid.Parse("E0A7DFA1-6B8A-4BD8-812C-54D7CBFAA394");
+        return Guid.Parse("00000000-0000-0000-0000-000000000001");
 
         // TODO: 恢復真實認證後改回 JWT Token 解析
         // var userIdClaim = User.FindFirst(ClaimTypes.NameIdentifier)?.Value
diff --git a/backend/DramaLing.Api/Controllers/StatsController.cs b/backend/DramaLing.Api/Controllers/StatsController.cs
index 9cb7445..95c17cd 100644
--- a/backend/DramaLing.Api/Controllers/StatsController.cs
+++ b/backend/DramaLing.Api/Controllers/StatsController.cs
@@ -1,6 +1,7 @@
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.EntityFrameworkCore;
 using DramaLing.Api.Data;
+using DramaLing.Api.Utils;
 using Microsoft.AspNetCore.Authorization;
 using System.Security.Claims;
 
@@ -217,10 +218,13 @@ public class StatsController : BaseController
                 .Where(f => f.UserId == userId)
                 .ToListAsync();
 
-            // 按難度分類
+            // 按難度分類 - 使用數字等級進行統計，更高效
             var difficultyStats = flashcards
-                .GroupBy(f => f.DifficultyLevel ?? "unknown")
-                .ToDictionary(g => g.Key, g => g.Count());
+                .GroupBy(f => f.DifficultyLevelNumeric)
+                .ToDictionary(
+                    g => g.Key == 0 ? "unknown" : CEFRHelper.ToString(g.Key),
+                    g => g.Count()
+                );
 
             // 按詞性分類
             var partOfSpeechStats = flashcards
diff --git a/backend/DramaLing.Api/Data/DramaLingDbContext.cs b/backend/DramaLing.Api/Data/DramaLingDbContext.cs
index f91ec61..3e8fd10 100644
--- a/backend/DramaLing.Api/Data/DramaLingDbContext.cs
+++ b/backend/DramaLing.Api/Data/DramaLingDbContext.cs
@@ -99,6 +99,9 @@ public class DramaLingDbContext : DbContext
 
         // 新增個人化欄位映射
         userEntity.Property(u => u.EnglishLevel).HasColumnName("english_level");
+        userEntity.Property(u => u.EnglishLevelNumeric)
+            .HasColumnName("english_level_numeric")
+            .HasDefaultValue(2); // 預設 A2
         userEntity.Property(u => u.LevelUpdatedAt).HasColumnName("level_updated_at");
         userEntity.Property(u => u.IsLevelVerified).HasColumnName("is_level_verified");
         userEntity.Property(u => u.LevelNotes).HasColumnName("level_notes");
@@ -128,7 +131,10 @@ public class DramaLingDbContext : DbContext
         // TimesReviewed, TimesCorrect, LastReviewedAt 已移除
         flashcardEntity.Property(f => f.IsFavorite).HasColumnName("is_favorite");
         flashcardEntity.Property(f => f.IsArchived).HasColumnName("is_archived");
-        flashcardEntity.Property(f => f.DifficultyLevel).HasColumnName("difficulty_level");
+
+        // 難度等級映射 - 使用數字格式
+        flashcardEntity.Property(f => f.DifficultyLevelNumeric).HasColumnName("difficulty_level_numeric");
+
         flashcardEntity.Property(f => f.CreatedAt).HasColumnName("created_at");
         flashcardEntity.Property(f => f.UpdatedAt).HasColumnName("updated_at");
     }
diff --git a/backend/DramaLing.Api/Extensions/ServiceCollectionExtensions.cs b/backend/DramaLing.Api/Extensions/ServiceCollectionExtensions.cs
index 1dbb05b..98f4bce 100644
--- a/backend/DramaLing.Api/Extensions/ServiceCollectionExtensions.cs
+++ b/backend/DramaLing.Api/Extensions/ServiceCollectionExtensions.cs
@@ -124,6 +124,7 @@ public static class ServiceCollectionExtensions
         services.AddScoped<IImageSaveManager, ImageSaveManager>();
         services.AddScoped<IGenerationPipelineService, GenerationPipelineService>();
         services.AddScoped<IImageGenerationWorkflow, ImageGenerationWorkflow>();
+        services.AddScoped<IImageGenerationOrchestrator, ImageGenerationOrchestrator>();
 
         return services;
     }
diff --git a/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.Designer.cs b/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.Designer.cs
new file mode 100644
index 0000000..e4ccf24
--- /dev/null
+++ b/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.Designer.cs
@@ -0,0 +1,1256 @@
+// <auto-generated />
+using System;
+using DramaLing.Api.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace DramaLing.Api.Migrations
+{
+    [DbContext(typeof(DramaLingDbContext))]
+    [Migration("20250930113251_AddDifficultyLevelNumeric")]
+    partial class AddDifficultyLevelNumeric
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "8.0.10");
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.AudioCache", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Accent")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("accent");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AudioUrl")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("audio_url");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int?>("DurationMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("duration_ms");
+
+                    b.Property<int?>("FileSize")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("file_size");
+
+                    b.Property<DateTime>("LastAccessed")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("last_accessed");
+
+                    b.Property<string>("TextContent")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("text_content");
+
+                    b.Property<string>("TextHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("text_hash");
+
+                    b.Property<string>("VoiceId")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("voice_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("LastAccessed")
+                        .HasDatabaseName("IX_AudioCache_LastAccessed");
+
+                    b.HasIndex("TextHash")
+                        .IsUnique()
+                        .HasDatabaseName("IX_AudioCache_TextHash");
+
+                    b.ToTable("audio_cache", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.DailyStats", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AiApiCalls")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("ai_api_calls");
+
+                    b.Property<int>("CardsGenerated")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("cards_generated");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("date");
+
+                    b.Property<int>("SessionCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("session_count");
+
+                    b.Property<int>("StudyTimeSeconds")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("study_time_seconds");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<int>("WordsCorrect")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("words_correct");
+
+                    b.Property<int>("WordsStudied")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("words_studied");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId", "Date")
+                        .IsUnique();
+
+                    b.ToTable("daily_stats", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ErrorReport", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("AdminNotes")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("admin_notes");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Description")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("description");
+
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<string>("ReportType")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("report_type");
+
+                    b.Property<DateTime?>("ResolvedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("resolved_at");
+
+                    b.Property<Guid?>("ResolvedBy")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("resolved_by");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("status");
+
+                    b.Property<string>("StudyMode")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("study_mode");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("ResolvedBy");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("error_reports", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ExampleImage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AltText")
+                        .HasMaxLength(200)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("alt_text");
+
+                    b.Property<string>("ContentHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("content_hash");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int?>("FileSize")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("file_size");
+
+                    b.Property<decimal?>("GeminiCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_cost");
+
+                    b.Property<string>("GeminiDescription")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_description");
+
+                    b.Property<string>("GeminiPrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_prompt");
+
+                    b.Property<int?>("ImageHeight")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("image_height");
+
+                    b.Property<int?>("ImageWidth")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("image_width");
+
+                    b.Property<string>("ModerationNotes")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("moderation_notes");
+
+                    b.Property<string>("ModerationStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("moderation_status");
+
+                    b.Property<decimal?>("QualityScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("quality_score");
+
+                    b.Property<string>("RelativePath")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("relative_path");
+
+                    b.Property<decimal?>("ReplicateCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_cost");
+
+                    b.Property<string>("ReplicateModel")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_model");
+
+                    b.Property<string>("ReplicatePrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_prompt");
+
+                    b.Property<string>("ReplicateVersion")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_version");
+
+                    b.Property<decimal?>("TotalGenerationCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("total_generation_cost");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AccessCount");
+
+                    b.HasIndex("ContentHash")
+                        .IsUnique();
+
+                    b.ToTable("example_images", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Definition")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("definition");
+
+                    b.Property<string>("DifficultyLevel")
+                        .HasMaxLength(10)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("difficulty_level");
+
+                    b.Property<int>("DifficultyLevelNumeric")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("difficulty_level_numeric");
+
+                    b.Property<string>("Example")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example");
+
+                    b.Property<string>("ExampleTranslation")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example_translation");
+
+                    b.Property<bool>("IsArchived")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_archived");
+
+                    b.Property<bool>("IsFavorite")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_favorite");
+
+                    b.Property<string>("PartOfSpeech")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("part_of_speech");
+
+                    b.Property<string>("Pronunciation")
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("pronunciation");
+
+                    b.Property<string>("Translation")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("translation");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<string>("Word")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("word");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("flashcards", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardExampleImage", b =>
+                {
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<Guid>("ExampleImageId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example_image_id");
+
+                    b.Property<decimal?>("ContextRelevance")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("context_relevance");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int>("DisplayOrder")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("display_order");
+
+                    b.Property<bool>("IsPrimary")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_primary");
+
+                    b.HasKey("FlashcardId", "ExampleImageId");
+
+                    b.HasIndex("ExampleImageId");
+
+                    b.ToTable("flashcard_example_images", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardTag", b =>
+                {
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<Guid>("TagId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("tag_id");
+
+                    b.HasKey("FlashcardId", "TagId");
+
+                    b.HasIndex("TagId");
+
+                    b.ToTable("flashcard_tags", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ImageGenerationRequest", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime?>("CompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("completed_at");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("FinalReplicatePrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("final_replicate_prompt");
+
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<DateTime?>("GeminiCompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_completed_at");
+
+                    b.Property<decimal?>("GeminiCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_cost");
+
+                    b.Property<string>("GeminiErrorMessage")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_error_message");
+
+                    b.Property<int?>("GeminiProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("gemini_processing_time_ms");
+
+                    b.Property<string>("GeminiPrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_prompt");
+
+                    b.Property<DateTime?>("GeminiStartedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_started_at");
+
+                    b.Property<string>("GeminiStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_status");
+
+                    b.Property<string>("GeneratedDescription")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("generated_description");
+
+                    b.Property<Guid?>("GeneratedImageId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("generated_image_id");
+
+                    b.Property<string>("OriginalRequest")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("original_request");
+
+                    b.Property<string>("OverallStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("overall_status");
+
+                    b.Property<DateTime?>("ReplicateCompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_completed_at");
+
+                    b.Property<decimal?>("ReplicateCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_cost");
+
+                    b.Property<string>("ReplicateErrorMessage")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_error_message");
+
+                    b.Property<int?>("ReplicateProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("replicate_processing_time_ms");
+
+                    b.Property<DateTime?>("ReplicateStartedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_started_at");
+
+                    b.Property<string>("ReplicateStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_status");
+
+                    b.Property<decimal?>("TotalCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("total_cost");
+
+                    b.Property<int?>("TotalProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("total_processing_time_ms");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("GeneratedImageId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("image_generation_requests", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.OptionsVocabulary", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("CEFRLevel")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("cefr_level");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at")
+                        .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+                    b.Property<bool>("IsActive")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(true)
+                        .HasColumnName("is_active");
+
+                    b.Property<string>("PartOfSpeech")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("part_of_speech");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at")
+                        .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+                    b.Property<string>("Word")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("word");
+
+                    b.Property<int>("WordLength")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("word_length");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex(new[] { "IsActive" }, "IX_OptionsVocabulary_Active");
+
+                    b.HasIndex(new[] { "CEFRLevel" }, "IX_OptionsVocabulary_CEFR");
+
+                    b.HasIndex(new[] { "CEFRLevel", "PartOfSpeech", "WordLength" }, "IX_OptionsVocabulary_Core_Matching");
+
+                    b.HasIndex(new[] { "PartOfSpeech" }, "IX_OptionsVocabulary_PartOfSpeech");
+
+                    b.HasIndex(new[] { "Word" }, "IX_OptionsVocabulary_Word")
+                        .IsUnique();
+
+                    b.HasIndex(new[] { "WordLength" }, "IX_OptionsVocabulary_WordLength");
+
+                    b.ToTable("options_vocabularies", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.PronunciationAssessment", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<decimal>("AccuracyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("accuracy_score");
+
+                    b.Property<string>("AudioUrl")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("audio_url");
+
+                    b.Property<decimal>("CompletenessScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("completeness_score");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<Guid?>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<decimal>("FluencyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("fluency_score");
+
+                    b.Property<int>("OverallScore")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("overall_score");
+
+                    b.Property<string>("PhonemeScores")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("phoneme_scores");
+
+                    b.Property<string>("PracticeMode")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("practice_mode");
+
+                    b.Property<decimal>("ProsodyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("prosody_score");
+
+                    b.Property<string>("Suggestions")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("suggestions");
+
+                    b.Property<string>("TargetText")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("target_text");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("UserId", "FlashcardId")
+                        .HasDatabaseName("IX_PronunciationAssessment_UserFlashcard");
+
+                    b.ToTable("pronunciation_assessments", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.SentenceAnalysisCache", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AnalysisResult")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("analysis_result");
+
+                    b.Property<string>("CorrectedText")
+                        .HasMaxLength(1000)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("corrected_text");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateTime>("ExpiresAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("expires_at");
+
+                    b.Property<string>("GrammarCorrections")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("grammar_corrections");
+
+                    b.Property<bool>("HasGrammarErrors")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("has_grammar_errors");
+
+                    b.Property<string>("HighValueWords")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("high_value_words");
+
+                    b.Property<string>("IdiomsDetected")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("idioms_detected");
+
+                    b.Property<string>("InputText")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("input_text");
+
+                    b.Property<string>("InputTextHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("input_text_hash");
+
+                    b.Property<DateTime?>("LastAccessedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("last_accessed_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ExpiresAt")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Expires");
+
+                    b.HasIndex("InputTextHash")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Hash");
+
+                    b.HasIndex("InputTextHash", "ExpiresAt")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Hash_Expires");
+
+                    b.ToTable("sentence_analysis_cache", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Color")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("color");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("name");
+
+                    b.Property<int>("UsageCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("usage_count");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("tags", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.User", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("AvatarUrl")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("avatar_url");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("display_name");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("email");
+
+                    b.Property<string>("EnglishLevel")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("english_level");
+
+                    b.Property<bool>("IsLevelVerified")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_level_verified");
+
+                    b.Property<string>("LevelNotes")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("level_notes");
+
+                    b.Property<DateTime>("LevelUpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("level_updated_at");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("password_hash");
+
+                    b.Property<string>("Preferences")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferences");
+
+                    b.Property<string>("SubscriptionType")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("subscription_type");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("username");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Email")
+                        .IsUnique();
+
+                    b.HasIndex("Username")
+                        .IsUnique();
+
+                    b.ToTable("user_profiles", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserAudioPreferences", b =>
+                {
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<bool>("AutoPlayEnabled")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("auto_play_enabled");
+
+                    b.Property<decimal>("DefaultSpeed")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("default_speed");
+
+                    b.Property<bool>("EnableDetailedFeedback")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("enable_detailed_feedback");
+
+                    b.Property<string>("PreferredAccent")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_accent");
+
+                    b.Property<string>("PreferredVoiceFemale")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_voice_female");
+
+                    b.Property<string>("PreferredVoiceMale")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_voice_male");
+
+                    b.Property<string>("PronunciationDifficulty")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("pronunciation_difficulty");
+
+                    b.Property<int>("TargetScoreThreshold")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("target_score_threshold");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("UserId");
+
+                    b.ToTable("user_audio_preferences", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserSettings", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<bool>("AutoPlayAudio")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("auto_play_audio");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int>("DailyGoal")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("daily_goal");
+
+                    b.Property<string>("DifficultyPreference")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("difficulty_preference");
+
+                    b.Property<bool>("ReminderEnabled")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("reminder_enabled");
+
+                    b.Property<TimeOnly>("ReminderTime")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("reminder_time");
+
+                    b.Property<bool>("ShowPronunciation")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("show_pronunciation");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId")
+                        .IsUnique();
+
+                    b.ToTable("user_settings", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.WordQueryUsageStats", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("date");
+
+                    b.Property<int>("HighValueWordClicks")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("high_value_word_clicks");
+
+                    b.Property<int>("LowValueWordClicks")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("low_value_word_clicks");
+
+                    b.Property<int>("SentenceAnalysisCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("sentence_analysis_count");
+
+                    b.Property<int>("TotalApiCalls")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("total_api_calls");
+
+                    b.Property<int>("UniqueWordsQueried")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("unique_words_queried");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt")
+                        .HasDatabaseName("IX_WordQueryUsageStats_CreatedAt");
+
+                    b.HasIndex("UserId", "Date")
+                        .IsUnique()
+                        .HasDatabaseName("IX_WordQueryUsageStats_UserDate");
+
+                    b.ToTable("word_query_usage_stats", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.DailyStats", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("DailyStats")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ErrorReport", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("ErrorReports")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "ResolvedByUser")
+                        .WithMany()
+                        .HasForeignKey("ResolvedBy")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("ErrorReports")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("ResolvedByUser");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("Flashcards")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardExampleImage", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.ExampleImage", "ExampleImage")
+                        .WithMany("FlashcardExampleImages")
+                        .HasForeignKey("ExampleImageId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("FlashcardExampleImages")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("ExampleImage");
+
+                    b.Navigation("Flashcard");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardTag", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("FlashcardTags")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.Tag", "Tag")
+                        .WithMany("FlashcardTags")
+                        .HasForeignKey("TagId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("Tag");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ImageGenerationRequest", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany()
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.ExampleImage", "GeneratedImage")
+                        .WithMany()
+                        .HasForeignKey("GeneratedImageId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("GeneratedImage");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.PronunciationAssessment", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany()
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserAudioPreferences", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithOne()
+                        .HasForeignKey("DramaLing.Api.Models.Entities.UserAudioPreferences", "UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserSettings", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithOne("Settings")
+                        .HasForeignKey("DramaLing.Api.Models.Entities.UserSettings", "UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.WordQueryUsageStats", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ExampleImage", b =>
+                {
+                    b.Navigation("FlashcardExampleImages");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.Navigation("ErrorReports");
+
+                    b.Navigation("FlashcardExampleImages");
+
+                    b.Navigation("FlashcardTags");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.Navigation("FlashcardTags");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.User", b =>
+                {
+                    b.Navigation("DailyStats");
+
+                    b.Navigation("ErrorReports");
+
+                    b.Navigation("Flashcards");
+
+                    b.Navigation("Settings");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}
diff --git a/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.cs b/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.cs
new file mode 100644
index 0000000..dcff9c9
--- /dev/null
+++ b/backend/DramaLing.Api/Migrations/20250930113251_AddDifficultyLevelNumeric.cs
@@ -0,0 +1,46 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace DramaLing.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddDifficultyLevelNumeric : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            // 1. 新增數字欄位 (預設值為 0)
+            migrationBuilder.AddColumn<int>(
+                name: "difficulty_level_numeric",
+                table: "flashcards",
+                type: "INTEGER",
+                nullable: false,
+                defaultValue: 0);
+
+            // 2. 資料遷移：將現有字串值轉換為數字
+            migrationBuilder.Sql(@"
+                UPDATE flashcards
+                SET difficulty_level_numeric =
+                    CASE difficulty_level
+                        WHEN 'A1' THEN 1
+                        WHEN 'A2' THEN 2
+                        WHEN 'B1' THEN 3
+                        WHEN 'B2' THEN 4
+                        WHEN 'C1' THEN 5
+                        WHEN 'C2' THEN 6
+                        ELSE 0
+                    END
+                WHERE difficulty_level IS NOT NULL;
+            ");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "difficulty_level_numeric",
+                table: "flashcards");
+        }
+    }
+}
diff --git a/backend/DramaLing.Api/Migrations/20250930145636_RemoveDifficultyLevelStringColumn.Designer.cs b/backend/DramaLing.Api/Migrations/20250930145636_RemoveDifficultyLevelStringColumn.Designer.cs
new file mode 100644
index 0000000..663df26
--- /dev/null
+++ b/backend/DramaLing.Api/Migrations/20250930145636_RemoveDifficultyLevelStringColumn.Designer.cs
@@ -0,0 +1,1251 @@
+// <auto-generated />
+using System;
+using DramaLing.Api.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace DramaLing.Api.Migrations
+{
+    [DbContext(typeof(DramaLingDbContext))]
+    [Migration("20250930145636_RemoveDifficultyLevelStringColumn")]
+    partial class RemoveDifficultyLevelStringColumn
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "8.0.10");
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.AudioCache", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Accent")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("accent");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AudioUrl")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("audio_url");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int?>("DurationMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("duration_ms");
+
+                    b.Property<int?>("FileSize")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("file_size");
+
+                    b.Property<DateTime>("LastAccessed")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("last_accessed");
+
+                    b.Property<string>("TextContent")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("text_content");
+
+                    b.Property<string>("TextHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("text_hash");
+
+                    b.Property<string>("VoiceId")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("voice_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("LastAccessed")
+                        .HasDatabaseName("IX_AudioCache_LastAccessed");
+
+                    b.HasIndex("TextHash")
+                        .IsUnique()
+                        .HasDatabaseName("IX_AudioCache_TextHash");
+
+                    b.ToTable("audio_cache", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.DailyStats", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AiApiCalls")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("ai_api_calls");
+
+                    b.Property<int>("CardsGenerated")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("cards_generated");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("date");
+
+                    b.Property<int>("SessionCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("session_count");
+
+                    b.Property<int>("StudyTimeSeconds")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("study_time_seconds");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<int>("WordsCorrect")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("words_correct");
+
+                    b.Property<int>("WordsStudied")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("words_studied");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId", "Date")
+                        .IsUnique();
+
+                    b.ToTable("daily_stats", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ErrorReport", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("AdminNotes")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("admin_notes");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Description")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("description");
+
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<string>("ReportType")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("report_type");
+
+                    b.Property<DateTime?>("ResolvedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("resolved_at");
+
+                    b.Property<Guid?>("ResolvedBy")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("resolved_by");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("status");
+
+                    b.Property<string>("StudyMode")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("study_mode");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("ResolvedBy");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("error_reports", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ExampleImage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AltText")
+                        .HasMaxLength(200)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("alt_text");
+
+                    b.Property<string>("ContentHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("content_hash");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int?>("FileSize")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("file_size");
+
+                    b.Property<decimal?>("GeminiCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_cost");
+
+                    b.Property<string>("GeminiDescription")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_description");
+
+                    b.Property<string>("GeminiPrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_prompt");
+
+                    b.Property<int?>("ImageHeight")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("image_height");
+
+                    b.Property<int?>("ImageWidth")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("image_width");
+
+                    b.Property<string>("ModerationNotes")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("moderation_notes");
+
+                    b.Property<string>("ModerationStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("moderation_status");
+
+                    b.Property<decimal?>("QualityScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("quality_score");
+
+                    b.Property<string>("RelativePath")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("relative_path");
+
+                    b.Property<decimal?>("ReplicateCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_cost");
+
+                    b.Property<string>("ReplicateModel")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_model");
+
+                    b.Property<string>("ReplicatePrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_prompt");
+
+                    b.Property<string>("ReplicateVersion")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_version");
+
+                    b.Property<decimal?>("TotalGenerationCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("total_generation_cost");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AccessCount");
+
+                    b.HasIndex("ContentHash")
+                        .IsUnique();
+
+                    b.ToTable("example_images", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Definition")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("definition");
+
+                    b.Property<int>("DifficultyLevelNumeric")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("difficulty_level_numeric");
+
+                    b.Property<string>("Example")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example");
+
+                    b.Property<string>("ExampleTranslation")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example_translation");
+
+                    b.Property<bool>("IsArchived")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_archived");
+
+                    b.Property<bool>("IsFavorite")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_favorite");
+
+                    b.Property<string>("PartOfSpeech")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("part_of_speech");
+
+                    b.Property<string>("Pronunciation")
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("pronunciation");
+
+                    b.Property<string>("Translation")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("translation");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<string>("Word")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("word");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("flashcards", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardExampleImage", b =>
+                {
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<Guid>("ExampleImageId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example_image_id");
+
+                    b.Property<decimal?>("ContextRelevance")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("context_relevance");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int>("DisplayOrder")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("display_order");
+
+                    b.Property<bool>("IsPrimary")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_primary");
+
+                    b.HasKey("FlashcardId", "ExampleImageId");
+
+                    b.HasIndex("ExampleImageId");
+
+                    b.ToTable("flashcard_example_images", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardTag", b =>
+                {
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<Guid>("TagId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("tag_id");
+
+                    b.HasKey("FlashcardId", "TagId");
+
+                    b.HasIndex("TagId");
+
+                    b.ToTable("flashcard_tags", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ImageGenerationRequest", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime?>("CompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("completed_at");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("FinalReplicatePrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("final_replicate_prompt");
+
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<DateTime?>("GeminiCompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_completed_at");
+
+                    b.Property<decimal?>("GeminiCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_cost");
+
+                    b.Property<string>("GeminiErrorMessage")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_error_message");
+
+                    b.Property<int?>("GeminiProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("gemini_processing_time_ms");
+
+                    b.Property<string>("GeminiPrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_prompt");
+
+                    b.Property<DateTime?>("GeminiStartedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_started_at");
+
+                    b.Property<string>("GeminiStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_status");
+
+                    b.Property<string>("GeneratedDescription")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("generated_description");
+
+                    b.Property<Guid?>("GeneratedImageId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("generated_image_id");
+
+                    b.Property<string>("OriginalRequest")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("original_request");
+
+                    b.Property<string>("OverallStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("overall_status");
+
+                    b.Property<DateTime?>("ReplicateCompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_completed_at");
+
+                    b.Property<decimal?>("ReplicateCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_cost");
+
+                    b.Property<string>("ReplicateErrorMessage")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_error_message");
+
+                    b.Property<int?>("ReplicateProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("replicate_processing_time_ms");
+
+                    b.Property<DateTime?>("ReplicateStartedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_started_at");
+
+                    b.Property<string>("ReplicateStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_status");
+
+                    b.Property<decimal?>("TotalCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("total_cost");
+
+                    b.Property<int?>("TotalProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("total_processing_time_ms");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("GeneratedImageId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("image_generation_requests", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.OptionsVocabulary", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("CEFRLevel")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("cefr_level");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at")
+                        .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+                    b.Property<bool>("IsActive")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(true)
+                        .HasColumnName("is_active");
+
+                    b.Property<string>("PartOfSpeech")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("part_of_speech");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at")
+                        .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+                    b.Property<string>("Word")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("word");
+
+                    b.Property<int>("WordLength")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("word_length");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex(new[] { "IsActive" }, "IX_OptionsVocabulary_Active");
+
+                    b.HasIndex(new[] { "CEFRLevel" }, "IX_OptionsVocabulary_CEFR");
+
+                    b.HasIndex(new[] { "CEFRLevel", "PartOfSpeech", "WordLength" }, "IX_OptionsVocabulary_Core_Matching");
+
+                    b.HasIndex(new[] { "PartOfSpeech" }, "IX_OptionsVocabulary_PartOfSpeech");
+
+                    b.HasIndex(new[] { "Word" }, "IX_OptionsVocabulary_Word")
+                        .IsUnique();
+
+                    b.HasIndex(new[] { "WordLength" }, "IX_OptionsVocabulary_WordLength");
+
+                    b.ToTable("options_vocabularies", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.PronunciationAssessment", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<decimal>("AccuracyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("accuracy_score");
+
+                    b.Property<string>("AudioUrl")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("audio_url");
+
+                    b.Property<decimal>("CompletenessScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("completeness_score");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<Guid?>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<decimal>("FluencyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("fluency_score");
+
+                    b.Property<int>("OverallScore")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("overall_score");
+
+                    b.Property<string>("PhonemeScores")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("phoneme_scores");
+
+                    b.Property<string>("PracticeMode")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("practice_mode");
+
+                    b.Property<decimal>("ProsodyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("prosody_score");
+
+                    b.Property<string>("Suggestions")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("suggestions");
+
+                    b.Property<string>("TargetText")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("target_text");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("UserId", "FlashcardId")
+                        .HasDatabaseName("IX_PronunciationAssessment_UserFlashcard");
+
+                    b.ToTable("pronunciation_assessments", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.SentenceAnalysisCache", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AnalysisResult")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("analysis_result");
+
+                    b.Property<string>("CorrectedText")
+                        .HasMaxLength(1000)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("corrected_text");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateTime>("ExpiresAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("expires_at");
+
+                    b.Property<string>("GrammarCorrections")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("grammar_corrections");
+
+                    b.Property<bool>("HasGrammarErrors")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("has_grammar_errors");
+
+                    b.Property<string>("HighValueWords")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("high_value_words");
+
+                    b.Property<string>("IdiomsDetected")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("idioms_detected");
+
+                    b.Property<string>("InputText")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("input_text");
+
+                    b.Property<string>("InputTextHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("input_text_hash");
+
+                    b.Property<DateTime?>("LastAccessedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("last_accessed_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ExpiresAt")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Expires");
+
+                    b.HasIndex("InputTextHash")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Hash");
+
+                    b.HasIndex("InputTextHash", "ExpiresAt")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Hash_Expires");
+
+                    b.ToTable("sentence_analysis_cache", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Color")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("color");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("name");
+
+                    b.Property<int>("UsageCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("usage_count");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("tags", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.User", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("AvatarUrl")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("avatar_url");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("display_name");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("email");
+
+                    b.Property<string>("EnglishLevel")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("english_level");
+
+                    b.Property<bool>("IsLevelVerified")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_level_verified");
+
+                    b.Property<string>("LevelNotes")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("level_notes");
+
+                    b.Property<DateTime>("LevelUpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("level_updated_at");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("password_hash");
+
+                    b.Property<string>("Preferences")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferences");
+
+                    b.Property<string>("SubscriptionType")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("subscription_type");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("username");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Email")
+                        .IsUnique();
+
+                    b.HasIndex("Username")
+                        .IsUnique();
+
+                    b.ToTable("user_profiles", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserAudioPreferences", b =>
+                {
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<bool>("AutoPlayEnabled")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("auto_play_enabled");
+
+                    b.Property<decimal>("DefaultSpeed")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("default_speed");
+
+                    b.Property<bool>("EnableDetailedFeedback")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("enable_detailed_feedback");
+
+                    b.Property<string>("PreferredAccent")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_accent");
+
+                    b.Property<string>("PreferredVoiceFemale")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_voice_female");
+
+                    b.Property<string>("PreferredVoiceMale")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_voice_male");
+
+                    b.Property<string>("PronunciationDifficulty")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("pronunciation_difficulty");
+
+                    b.Property<int>("TargetScoreThreshold")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("target_score_threshold");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("UserId");
+
+                    b.ToTable("user_audio_preferences", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserSettings", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<bool>("AutoPlayAudio")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("auto_play_audio");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int>("DailyGoal")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("daily_goal");
+
+                    b.Property<string>("DifficultyPreference")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("difficulty_preference");
+
+                    b.Property<bool>("ReminderEnabled")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("reminder_enabled");
+
+                    b.Property<TimeOnly>("ReminderTime")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("reminder_time");
+
+                    b.Property<bool>("ShowPronunciation")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("show_pronunciation");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId")
+                        .IsUnique();
+
+                    b.ToTable("user_settings", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.WordQueryUsageStats", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("date");
+
+                    b.Property<int>("HighValueWordClicks")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("high_value_word_clicks");
+
+                    b.Property<int>("LowValueWordClicks")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("low_value_word_clicks");
+
+                    b.Property<int>("SentenceAnalysisCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("sentence_analysis_count");
+
+                    b.Property<int>("TotalApiCalls")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("total_api_calls");
+
+                    b.Property<int>("UniqueWordsQueried")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("unique_words_queried");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt")
+                        .HasDatabaseName("IX_WordQueryUsageStats_CreatedAt");
+
+                    b.HasIndex("UserId", "Date")
+                        .IsUnique()
+                        .HasDatabaseName("IX_WordQueryUsageStats_UserDate");
+
+                    b.ToTable("word_query_usage_stats", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.DailyStats", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("DailyStats")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ErrorReport", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("ErrorReports")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "ResolvedByUser")
+                        .WithMany()
+                        .HasForeignKey("ResolvedBy")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("ErrorReports")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("ResolvedByUser");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("Flashcards")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardExampleImage", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.ExampleImage", "ExampleImage")
+                        .WithMany("FlashcardExampleImages")
+                        .HasForeignKey("ExampleImageId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("FlashcardExampleImages")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("ExampleImage");
+
+                    b.Navigation("Flashcard");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardTag", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("FlashcardTags")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.Tag", "Tag")
+                        .WithMany("FlashcardTags")
+                        .HasForeignKey("TagId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("Tag");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ImageGenerationRequest", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany()
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.ExampleImage", "GeneratedImage")
+                        .WithMany()
+                        .HasForeignKey("GeneratedImageId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("GeneratedImage");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.PronunciationAssessment", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany()
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserAudioPreferences", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithOne()
+                        .HasForeignKey("DramaLing.Api.Models.Entities.UserAudioPreferences", "UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserSettings", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithOne("Settings")
+                        .HasForeignKey("DramaLing.Api.Models.Entities.UserSettings", "UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.WordQueryUsageStats", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ExampleImage", b =>
+                {
+                    b.Navigation("FlashcardExampleImages");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.Navigation("ErrorReports");
+
+                    b.Navigation("FlashcardExampleImages");
+
+                    b.Navigation("FlashcardTags");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.Navigation("FlashcardTags");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.User", b =>
+                {
+                    b.Navigation("DailyStats");
+
+                    b.Navigation("ErrorReports");
+
+                    b.Navigation("Flashcards");
+
+                    b.Navigation("Settings");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}
diff --git a/backend/DramaLing.Api/Migrations/20250930145636_RemoveDifficultyLevelStringColumn.cs b/backend/DramaLing.Api/Migrations/20250930145636_RemoveDifficultyLevelStringColumn.cs
new file mode 100644
index 0000000..546f032
--- /dev/null
+++ b/backend/DramaLing.Api/Migrations/20250930145636_RemoveDifficultyLevelStringColumn.cs
@@ -0,0 +1,29 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace DramaLing.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class RemoveDifficultyLevelStringColumn : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "difficulty_level",
+                table: "flashcards");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "difficulty_level",
+                table: "flashcards",
+                type: "TEXT",
+                maxLength: 10,
+                nullable: true);
+        }
+    }
+}
diff --git a/backend/DramaLing.Api/Migrations/20250930155857_AddEnglishLevelNumeric.Designer.cs b/backend/DramaLing.Api/Migrations/20250930155857_AddEnglishLevelNumeric.Designer.cs
new file mode 100644
index 0000000..a0428da
--- /dev/null
+++ b/backend/DramaLing.Api/Migrations/20250930155857_AddEnglishLevelNumeric.Designer.cs
@@ -0,0 +1,1257 @@
+// <auto-generated />
+using System;
+using DramaLing.Api.Data;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Microsoft.EntityFrameworkCore.Storage.ValueConversion;
+
+#nullable disable
+
+namespace DramaLing.Api.Migrations
+{
+    [DbContext(typeof(DramaLingDbContext))]
+    [Migration("20250930155857_AddEnglishLevelNumeric")]
+    partial class AddEnglishLevelNumeric
+    {
+        /// <inheritdoc />
+        protected override void BuildTargetModel(ModelBuilder modelBuilder)
+        {
+#pragma warning disable 612, 618
+            modelBuilder.HasAnnotation("ProductVersion", "8.0.10");
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.AudioCache", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Accent")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("accent");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AudioUrl")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("audio_url");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int?>("DurationMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("duration_ms");
+
+                    b.Property<int?>("FileSize")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("file_size");
+
+                    b.Property<DateTime>("LastAccessed")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("last_accessed");
+
+                    b.Property<string>("TextContent")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("text_content");
+
+                    b.Property<string>("TextHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("text_hash");
+
+                    b.Property<string>("VoiceId")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("voice_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("LastAccessed")
+                        .HasDatabaseName("IX_AudioCache_LastAccessed");
+
+                    b.HasIndex("TextHash")
+                        .IsUnique()
+                        .HasDatabaseName("IX_AudioCache_TextHash");
+
+                    b.ToTable("audio_cache", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.DailyStats", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AiApiCalls")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("ai_api_calls");
+
+                    b.Property<int>("CardsGenerated")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("cards_generated");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("date");
+
+                    b.Property<int>("SessionCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("session_count");
+
+                    b.Property<int>("StudyTimeSeconds")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("study_time_seconds");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<int>("WordsCorrect")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("words_correct");
+
+                    b.Property<int>("WordsStudied")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("words_studied");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId", "Date")
+                        .IsUnique();
+
+                    b.ToTable("daily_stats", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ErrorReport", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("AdminNotes")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("admin_notes");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Description")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("description");
+
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<string>("ReportType")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("report_type");
+
+                    b.Property<DateTime?>("ResolvedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("resolved_at");
+
+                    b.Property<Guid?>("ResolvedBy")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("resolved_by");
+
+                    b.Property<string>("Status")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("status");
+
+                    b.Property<string>("StudyMode")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("study_mode");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("ResolvedBy");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("error_reports", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ExampleImage", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AltText")
+                        .HasMaxLength(200)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("alt_text");
+
+                    b.Property<string>("ContentHash")
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("content_hash");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int?>("FileSize")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("file_size");
+
+                    b.Property<decimal?>("GeminiCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_cost");
+
+                    b.Property<string>("GeminiDescription")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_description");
+
+                    b.Property<string>("GeminiPrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_prompt");
+
+                    b.Property<int?>("ImageHeight")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("image_height");
+
+                    b.Property<int?>("ImageWidth")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("image_width");
+
+                    b.Property<string>("ModerationNotes")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("moderation_notes");
+
+                    b.Property<string>("ModerationStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("moderation_status");
+
+                    b.Property<decimal?>("QualityScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("quality_score");
+
+                    b.Property<string>("RelativePath")
+                        .IsRequired()
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("relative_path");
+
+                    b.Property<decimal?>("ReplicateCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_cost");
+
+                    b.Property<string>("ReplicateModel")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_model");
+
+                    b.Property<string>("ReplicatePrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_prompt");
+
+                    b.Property<string>("ReplicateVersion")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_version");
+
+                    b.Property<decimal?>("TotalGenerationCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("total_generation_cost");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("AccessCount");
+
+                    b.HasIndex("ContentHash")
+                        .IsUnique();
+
+                    b.ToTable("example_images", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Definition")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("definition");
+
+                    b.Property<int>("DifficultyLevelNumeric")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("difficulty_level_numeric");
+
+                    b.Property<string>("Example")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example");
+
+                    b.Property<string>("ExampleTranslation")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example_translation");
+
+                    b.Property<bool>("IsArchived")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_archived");
+
+                    b.Property<bool>("IsFavorite")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_favorite");
+
+                    b.Property<string>("PartOfSpeech")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("part_of_speech");
+
+                    b.Property<string>("Pronunciation")
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("pronunciation");
+
+                    b.Property<string>("Translation")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("translation");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<string>("Word")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("word");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("flashcards", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardExampleImage", b =>
+                {
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<Guid>("ExampleImageId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("example_image_id");
+
+                    b.Property<decimal?>("ContextRelevance")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("context_relevance");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int>("DisplayOrder")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("display_order");
+
+                    b.Property<bool>("IsPrimary")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_primary");
+
+                    b.HasKey("FlashcardId", "ExampleImageId");
+
+                    b.HasIndex("ExampleImageId");
+
+                    b.ToTable("flashcard_example_images", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardTag", b =>
+                {
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<Guid>("TagId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("tag_id");
+
+                    b.HasKey("FlashcardId", "TagId");
+
+                    b.HasIndex("TagId");
+
+                    b.ToTable("flashcard_tags", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ImageGenerationRequest", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime?>("CompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("completed_at");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("FinalReplicatePrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("final_replicate_prompt");
+
+                    b.Property<Guid>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<DateTime?>("GeminiCompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_completed_at");
+
+                    b.Property<decimal?>("GeminiCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_cost");
+
+                    b.Property<string>("GeminiErrorMessage")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_error_message");
+
+                    b.Property<int?>("GeminiProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("gemini_processing_time_ms");
+
+                    b.Property<string>("GeminiPrompt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_prompt");
+
+                    b.Property<DateTime?>("GeminiStartedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_started_at");
+
+                    b.Property<string>("GeminiStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("gemini_status");
+
+                    b.Property<string>("GeneratedDescription")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("generated_description");
+
+                    b.Property<Guid?>("GeneratedImageId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("generated_image_id");
+
+                    b.Property<string>("OriginalRequest")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("original_request");
+
+                    b.Property<string>("OverallStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("overall_status");
+
+                    b.Property<DateTime?>("ReplicateCompletedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_completed_at");
+
+                    b.Property<decimal?>("ReplicateCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_cost");
+
+                    b.Property<string>("ReplicateErrorMessage")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_error_message");
+
+                    b.Property<int?>("ReplicateProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("replicate_processing_time_ms");
+
+                    b.Property<DateTime?>("ReplicateStartedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_started_at");
+
+                    b.Property<string>("ReplicateStatus")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("replicate_status");
+
+                    b.Property<decimal?>("TotalCost")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("total_cost");
+
+                    b.Property<int?>("TotalProcessingTimeMs")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("total_processing_time_ms");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("GeneratedImageId");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("image_generation_requests", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.OptionsVocabulary", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("CEFRLevel")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("cefr_level");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at")
+                        .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+                    b.Property<bool>("IsActive")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(true)
+                        .HasColumnName("is_active");
+
+                    b.Property<string>("PartOfSpeech")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("part_of_speech");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at")
+                        .HasDefaultValueSql("CURRENT_TIMESTAMP");
+
+                    b.Property<string>("Word")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("word");
+
+                    b.Property<int>("WordLength")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("word_length");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex(new[] { "IsActive" }, "IX_OptionsVocabulary_Active");
+
+                    b.HasIndex(new[] { "CEFRLevel" }, "IX_OptionsVocabulary_CEFR");
+
+                    b.HasIndex(new[] { "CEFRLevel", "PartOfSpeech", "WordLength" }, "IX_OptionsVocabulary_Core_Matching");
+
+                    b.HasIndex(new[] { "PartOfSpeech" }, "IX_OptionsVocabulary_PartOfSpeech");
+
+                    b.HasIndex(new[] { "Word" }, "IX_OptionsVocabulary_Word")
+                        .IsUnique();
+
+                    b.HasIndex(new[] { "WordLength" }, "IX_OptionsVocabulary_WordLength");
+
+                    b.ToTable("options_vocabularies", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.PronunciationAssessment", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<decimal>("AccuracyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("accuracy_score");
+
+                    b.Property<string>("AudioUrl")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("audio_url");
+
+                    b.Property<decimal>("CompletenessScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("completeness_score");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<Guid?>("FlashcardId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("flashcard_id");
+
+                    b.Property<decimal>("FluencyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("fluency_score");
+
+                    b.Property<int>("OverallScore")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("overall_score");
+
+                    b.Property<string>("PhonemeScores")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("phoneme_scores");
+
+                    b.Property<string>("PracticeMode")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("practice_mode");
+
+                    b.Property<decimal>("ProsodyScore")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("prosody_score");
+
+                    b.Property<string>("Suggestions")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("suggestions");
+
+                    b.Property<string>("TargetText")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("target_text");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("FlashcardId");
+
+                    b.HasIndex("UserId", "FlashcardId")
+                        .HasDatabaseName("IX_PronunciationAssessment_UserFlashcard");
+
+                    b.ToTable("pronunciation_assessments", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.SentenceAnalysisCache", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<int>("AccessCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("access_count");
+
+                    b.Property<string>("AnalysisResult")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("analysis_result");
+
+                    b.Property<string>("CorrectedText")
+                        .HasMaxLength(1000)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("corrected_text");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateTime>("ExpiresAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("expires_at");
+
+                    b.Property<string>("GrammarCorrections")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("grammar_corrections");
+
+                    b.Property<bool>("HasGrammarErrors")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("has_grammar_errors");
+
+                    b.Property<string>("HighValueWords")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("high_value_words");
+
+                    b.Property<string>("IdiomsDetected")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("idioms_detected");
+
+                    b.Property<string>("InputText")
+                        .IsRequired()
+                        .HasMaxLength(1000)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("input_text");
+
+                    b.Property<string>("InputTextHash")
+                        .IsRequired()
+                        .HasMaxLength(64)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("input_text_hash");
+
+                    b.Property<DateTime?>("LastAccessedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("last_accessed_at");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ExpiresAt")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Expires");
+
+                    b.HasIndex("InputTextHash")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Hash");
+
+                    b.HasIndex("InputTextHash", "ExpiresAt")
+                        .HasDatabaseName("IX_SentenceAnalysisCache_Hash_Expires");
+
+                    b.ToTable("sentence_analysis_cache", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("Color")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("color");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("Name")
+                        .IsRequired()
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("name");
+
+                    b.Property<int>("UsageCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("usage_count");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId");
+
+                    b.ToTable("tags", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.User", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<string>("AvatarUrl")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("avatar_url");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<string>("DisplayName")
+                        .HasMaxLength(100)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("display_name");
+
+                    b.Property<string>("Email")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("email");
+
+                    b.Property<string>("EnglishLevel")
+                        .IsRequired()
+                        .HasMaxLength(10)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("english_level");
+
+                    b.Property<int>("EnglishLevelNumeric")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(2)
+                        .HasColumnName("english_level_numeric");
+
+                    b.Property<bool>("IsLevelVerified")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("is_level_verified");
+
+                    b.Property<string>("LevelNotes")
+                        .HasMaxLength(500)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("level_notes");
+
+                    b.Property<DateTime>("LevelUpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("level_updated_at");
+
+                    b.Property<string>("PasswordHash")
+                        .IsRequired()
+                        .HasMaxLength(255)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("password_hash");
+
+                    b.Property<string>("Preferences")
+                        .IsRequired()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferences");
+
+                    b.Property<string>("SubscriptionType")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("subscription_type");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<string>("Username")
+                        .IsRequired()
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("username");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("Email")
+                        .IsUnique();
+
+                    b.HasIndex("Username")
+                        .IsUnique();
+
+                    b.ToTable("user_profiles", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserAudioPreferences", b =>
+                {
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.Property<bool>("AutoPlayEnabled")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("auto_play_enabled");
+
+                    b.Property<decimal>("DefaultSpeed")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("default_speed");
+
+                    b.Property<bool>("EnableDetailedFeedback")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("enable_detailed_feedback");
+
+                    b.Property<string>("PreferredAccent")
+                        .IsRequired()
+                        .HasMaxLength(2)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_accent");
+
+                    b.Property<string>("PreferredVoiceFemale")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_voice_female");
+
+                    b.Property<string>("PreferredVoiceMale")
+                        .HasMaxLength(50)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("preferred_voice_male");
+
+                    b.Property<string>("PronunciationDifficulty")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("pronunciation_difficulty");
+
+                    b.Property<int>("TargetScoreThreshold")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("target_score_threshold");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.HasKey("UserId");
+
+                    b.ToTable("user_audio_preferences", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserSettings", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<bool>("AutoPlayAudio")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("auto_play_audio");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<int>("DailyGoal")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("daily_goal");
+
+                    b.Property<string>("DifficultyPreference")
+                        .IsRequired()
+                        .HasMaxLength(20)
+                        .HasColumnType("TEXT")
+                        .HasColumnName("difficulty_preference");
+
+                    b.Property<bool>("ReminderEnabled")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("reminder_enabled");
+
+                    b.Property<TimeOnly>("ReminderTime")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("reminder_time");
+
+                    b.Property<bool>("ShowPronunciation")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("show_pronunciation");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("UserId")
+                        .IsUnique();
+
+                    b.ToTable("user_settings", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.WordQueryUsageStats", b =>
+                {
+                    b.Property<Guid>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("TEXT")
+                        .HasColumnName("id");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_at");
+
+                    b.Property<DateOnly>("Date")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("date");
+
+                    b.Property<int>("HighValueWordClicks")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("high_value_word_clicks");
+
+                    b.Property<int>("LowValueWordClicks")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("low_value_word_clicks");
+
+                    b.Property<int>("SentenceAnalysisCount")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("sentence_analysis_count");
+
+                    b.Property<int>("TotalApiCalls")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("total_api_calls");
+
+                    b.Property<int>("UniqueWordsQueried")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("unique_words_queried");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("updated_at");
+
+                    b.Property<Guid>("UserId")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("user_id");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("CreatedAt")
+                        .HasDatabaseName("IX_WordQueryUsageStats_CreatedAt");
+
+                    b.HasIndex("UserId", "Date")
+                        .IsUnique()
+                        .HasDatabaseName("IX_WordQueryUsageStats_UserDate");
+
+                    b.ToTable("word_query_usage_stats", (string)null);
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.DailyStats", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("DailyStats")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ErrorReport", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("ErrorReports")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "ResolvedByUser")
+                        .WithMany()
+                        .HasForeignKey("ResolvedBy")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("ErrorReports")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("ResolvedByUser");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany("Flashcards")
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardExampleImage", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.ExampleImage", "ExampleImage")
+                        .WithMany("FlashcardExampleImages")
+                        .HasForeignKey("ExampleImageId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("FlashcardExampleImages")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("ExampleImage");
+
+                    b.Navigation("Flashcard");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.FlashcardTag", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany("FlashcardTags")
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.Tag", "Tag")
+                        .WithMany("FlashcardTags")
+                        .HasForeignKey("TagId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("Tag");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ImageGenerationRequest", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany()
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.HasOne("DramaLing.Api.Models.Entities.ExampleImage", "GeneratedImage")
+                        .WithMany()
+                        .HasForeignKey("GeneratedImageId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("GeneratedImage");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.PronunciationAssessment", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.Flashcard", "Flashcard")
+                        .WithMany()
+                        .HasForeignKey("FlashcardId")
+                        .OnDelete(DeleteBehavior.SetNull);
+
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("Flashcard");
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserAudioPreferences", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithOne()
+                        .HasForeignKey("DramaLing.Api.Models.Entities.UserAudioPreferences", "UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.UserSettings", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithOne("Settings")
+                        .HasForeignKey("DramaLing.Api.Models.Entities.UserSettings", "UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.WordQueryUsageStats", b =>
+                {
+                    b.HasOne("DramaLing.Api.Models.Entities.User", "User")
+                        .WithMany()
+                        .HasForeignKey("UserId")
+                        .OnDelete(DeleteBehavior.Cascade)
+                        .IsRequired();
+
+                    b.Navigation("User");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.ExampleImage", b =>
+                {
+                    b.Navigation("FlashcardExampleImages");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Flashcard", b =>
+                {
+                    b.Navigation("ErrorReports");
+
+                    b.Navigation("FlashcardExampleImages");
+
+                    b.Navigation("FlashcardTags");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.Tag", b =>
+                {
+                    b.Navigation("FlashcardTags");
+                });
+
+            modelBuilder.Entity("DramaLing.Api.Models.Entities.User", b =>
+                {
+                    b.Navigation("DailyStats");
+
+                    b.Navigation("ErrorReports");
+
+                    b.Navigation("Flashcards");
+
+                    b.Navigation("Settings");
+                });
+#pragma warning restore 612, 618
+        }
+    }
+}
diff --git a/backend/DramaLing.Api/Migrations/20250930155857_AddEnglishLevelNumeric.cs b/backend/DramaLing.Api/Migrations/20250930155857_AddEnglishLevelNumeric.cs
new file mode 100644
index 0000000..8578c72
--- /dev/null
+++ b/backend/DramaLing.Api/Migrations/20250930155857_AddEnglishLevelNumeric.cs
@@ -0,0 +1,44 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace DramaLing.Api.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddEnglishLevelNumeric : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<int>(
+                name: "english_level_numeric",
+                table: "user_profiles",
+                type: "INTEGER",
+                nullable: false,
+                defaultValue: 2);
+
+            // 轉換現有資料：將字串格式的 english_level 轉換為數字格式
+            migrationBuilder.Sql(@"
+                UPDATE user_profiles
+                SET english_level_numeric =
+                    CASE english_level
+                        WHEN 'A1' THEN 1
+                        WHEN 'A2' THEN 2
+                        WHEN 'B1' THEN 3
+                        WHEN 'B2' THEN 4
+                        WHEN 'C1' THEN 5
+                        WHEN 'C2' THEN 6
+                        ELSE 2 -- 預設 A2
+                    END
+            ");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "english_level_numeric",
+                table: "user_profiles");
+        }
+    }
+}
diff --git a/backend/DramaLing.Api/Migrations/DramaLingDbContextModelSnapshot.cs b/backend/DramaLing.Api/Migrations/DramaLingDbContextModelSnapshot.cs
index 7382bec..50a696a 100644
--- a/backend/DramaLing.Api/Migrations/DramaLingDbContextModelSnapshot.cs
+++ b/backend/DramaLing.Api/Migrations/DramaLingDbContextModelSnapshot.cs
@@ -318,10 +318,9 @@ namespace DramaLing.Api.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("definition");
 
-                    b.Property<string>("DifficultyLevel")
-                        .HasMaxLength(10)
-                        .HasColumnType("TEXT")
-                        .HasColumnName("difficulty_level");
+                    b.Property<int>("DifficultyLevelNumeric")
+                        .HasColumnType("INTEGER")
+                        .HasColumnName("difficulty_level_numeric");
 
                     b.Property<string>("Example")
                         .HasColumnType("TEXT")
@@ -828,6 +827,12 @@ namespace DramaLing.Api.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("english_level");
 
+                    b.Property<int>("EnglishLevelNumeric")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("INTEGER")
+                        .HasDefaultValue(2)
+                        .HasColumnName("english_level_numeric");
+
                     b.Property<bool>("IsLevelVerified")
                         .HasColumnType("INTEGER")
                         .HasColumnName("is_level_verified");
diff --git a/backend/DramaLing.Api/Models/DTOs/AIAnalysisDto.cs b/backend/DramaLing.Api/Models/DTOs/AIAnalysisDto.cs
index 37cc6dc..3906b02 100644
--- a/backend/DramaLing.Api/Models/DTOs/AIAnalysisDto.cs
+++ b/backend/DramaLing.Api/Models/DTOs/AIAnalysisDto.cs
@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using DramaLing.Api.Utils;
 
 namespace DramaLing.Api.Models.DTOs;
 
@@ -73,7 +74,8 @@ public class VocabularyAnalysisDto
     public string Definition { get; set; } = string.Empty;
     public string PartOfSpeech { get; set; } = string.Empty;
     public string Pronunciation { get; set; } = string.Empty;
-    public string DifficultyLevel { get; set; } = string.Empty;
+    public int DifficultyLevelNumeric { get; set; }
+    public string CEFR { get; set; } = string.Empty;
     public string Frequency { get; set; } = string.Empty;
     public List<string> Synonyms { get; set; } = new();
     public string? Example { get; set; }
@@ -86,7 +88,8 @@ public class IdiomDto
     public string Translation { get; set; } = string.Empty;
     public string Definition { get; set; } = string.Empty;
     public string Pronunciation { get; set; } = string.Empty;
-    public string DifficultyLevel { get; set; } = string.Empty;
+    public int DifficultyLevelNumeric { get; set; }
+    public string CEFR { get; set; } = string.Empty;
     public string Frequency { get; set; } = string.Empty;
     public List<string> Synonyms { get; set; } = new();
     public string? Example { get; set; }
diff --git a/backend/DramaLing.Api/Models/DTOs/FlashcardDto.cs b/backend/DramaLing.Api/Models/DTOs/FlashcardDto.cs
index 761ab5f..5dc778f 100644
--- a/backend/DramaLing.Api/Models/DTOs/FlashcardDto.cs
+++ b/backend/DramaLing.Api/Models/DTOs/FlashcardDto.cs
@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using DramaLing.Api.Utils;
 
 namespace DramaLing.Api.Models.DTOs;
 
@@ -36,9 +37,11 @@ public class CreateFlashcardRequest
 
     public string? ExampleTranslation { get; set; }
 
-    [RegularExpression("^(A1|A2|B1|B2|C1|C2)$",
-                      ErrorMessage = "CEFR 等級必須為有效值")]
-    public string? DifficultyLevel { get; set; } = "A2";
+    // 雙軌制難度等級 - 支援字串和數字格式
+    [Range(0, 6, ErrorMessage = "難度等級必須在 0-6 之間")]
+    public int DifficultyLevelNumeric { get; set; } = 2; // 預設 A2 = 2
+
+    // 向後相容的字串格式，會自動從 DifficultyLevelNumeric 計算
 }
 
 public class UpdateFlashcardRequest : CreateFlashcardRequest
@@ -60,7 +63,11 @@ public class FlashcardResponse
     public int TimesReviewed { get; set; }
     public bool IsFavorite { get; set; }
     public DateTime NextReviewDate { get; set; }
+
+    // 雙軌制難度等級 - API 回應同時提供兩種格式
+    public int DifficultyLevelNumeric { get; set; }
     public string? DifficultyLevel { get; set; }
+
     public DateTime CreatedAt { get; set; }
     public DateTime? UpdatedAt { get; set; }
 }
diff --git a/backend/DramaLing.Api/Models/Entities/Flashcard.cs b/backend/DramaLing.Api/Models/Entities/Flashcard.cs
index 46430a0..12c8b74 100644
--- a/backend/DramaLing.Api/Models/Entities/Flashcard.cs
+++ b/backend/DramaLing.Api/Models/Entities/Flashcard.cs
@@ -1,12 +1,15 @@
 using System.ComponentModel.DataAnnotations;
+using DramaLing.Api.Utils;
 
 namespace DramaLing.Api.Models.Entities;
 
 /// <summary>
-/// 簡化的詞卡實體 - 移除所有複習功能
+/// 簡化的詞卡實體 - 使用數字難度等級
 /// </summary>
 public class Flashcard
 {
+    private int? _difficultyLevelNumeric;
+
     public Guid Id { get; set; }
 
     public Guid UserId { get; set; }
@@ -36,8 +39,14 @@ public class Flashcard
 
     public bool IsArchived { get; set; } = false;
 
-    [MaxLength(10)]
-    public string? DifficultyLevel { get; set; } // A1, A2, B1, B2, C1, C2
+    /// <summary>
+    /// CEFR 難度等級 (數字格式: 0=未知, 1=A1, 2=A2, 3=B1, 4=B2, 5=C1, 6=C2)
+    /// </summary>
+    public int DifficultyLevelNumeric
+    {
+        get => _difficultyLevelNumeric ?? 0;
+        set => _difficultyLevelNumeric = value;
+    }
 
     public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
     public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
diff --git a/backend/DramaLing.Api/Models/Entities/User.cs b/backend/DramaLing.Api/Models/Entities/User.cs
index 218fecf..7d6f137 100644
--- a/backend/DramaLing.Api/Models/Entities/User.cs
+++ b/backend/DramaLing.Api/Models/Entities/User.cs
@@ -1,4 +1,5 @@
 using System.ComponentModel.DataAnnotations;
+using DramaLing.Api.Utils;
 
 namespace DramaLing.Api.Models.Entities;
 
@@ -32,6 +33,11 @@ public class User
     [MaxLength(10)]
     public string EnglishLevel { get; set; } = "A2"; // A1, A2, B1, B2, C1, C2
 
+    /// <summary>
+    /// CEFR 英文程度等級 (數字格式: 0=未知, 1=A1, 2=A2, 3=B1, 4=B2, 5=C1, 6=C2)
+    /// </summary>
+    public int EnglishLevelNumeric { get; set; } = 2; // 預設 A2
+
     public DateTime LevelUpdatedAt { get; set; } = DateTime.UtcNow;
 
     public bool IsLevelVerified { get; set; } = false; // 是否通過測試驗證
diff --git a/backend/DramaLing.Api/Services/AI/Gemini/SentenceAnalyzer.cs b/backend/DramaLing.Api/Services/AI/Gemini/SentenceAnalyzer.cs
index fd42df0..9c7cdcd 100644
--- a/backend/DramaLing.Api/Services/AI/Gemini/SentenceAnalyzer.cs
+++ b/backend/DramaLing.Api/Services/AI/Gemini/SentenceAnalyzer.cs
@@ -1,4 +1,5 @@
 using DramaLing.Api.Models.DTOs;
+using DramaLing.Api.Utils;
 using System.Text.Json;
 
 namespace DramaLing.Api.Services.AI.Gemini;
@@ -84,7 +85,7 @@ public class SentenceAnalyzer : ISentenceAnalyzer
       ""definition"": ""English definition"",
       ""partOfSpeech"": ""noun/verb/adjective/adverb/pronoun/preposition/conjunction/interjection"",
       ""pronunciation"": ""/phonetic/"",
-      ""difficultyLevel"": ""A1/A2/B1/B2/C1/C2"",
+      ""CEFR"": ""A1/A2/B1/B2/C1/C2"",
       ""frequency"": ""high/medium/low"",
       ""synonyms"": [""synonym1"", ""synonym2""],
       ""example"": ""example sentence"",
@@ -97,7 +98,7 @@ public class SentenceAnalyzer : ISentenceAnalyzer
       ""translation"": ""Traditional Chinese meaning"",
       ""definition"": ""English explanation"",
       ""pronunciation"": ""/phonetic notation/"",
-      ""difficultyLevel"": ""A1/A2/B1/B2/C1/C2"",
+      ""CEFR"": ""A1/A2/B1/B2/C1/C2"",
       ""frequency"": ""high/medium/low"",
       ""synonyms"": [""synonym1"", ""synonym2""],
       ""example"": ""usage example"",
@@ -185,7 +186,8 @@ public class SentenceAnalyzer : ISentenceAnalyzer
                 Definition = aiWord.Definition ?? "",
                 PartOfSpeech = aiWord.PartOfSpeech ?? "unknown",
                 Pronunciation = aiWord.Pronunciation ?? $"/{kvp.Key}/",
-                DifficultyLevel = aiWord.DifficultyLevel ?? "A2",
+                DifficultyLevelNumeric = CEFRHelper.ToNumeric(aiWord.CEFR ?? "A0"),
+                CEFR = aiWord.CEFR ?? "A0",
                 Frequency = aiWord.Frequency ?? "medium",
                 Synonyms = aiWord.Synonyms ?? new List<string>(),
                 Example = aiWord.Example,
@@ -208,7 +210,8 @@ public class SentenceAnalyzer : ISentenceAnalyzer
                 Translation = aiIdiom.Translation ?? "",
                 Definition = aiIdiom.Definition ?? "",
                 Pronunciation = aiIdiom.Pronunciation ?? "",
-                DifficultyLevel = aiIdiom.DifficultyLevel ?? "B2",
+                DifficultyLevelNumeric = CEFRHelper.ToNumeric(aiIdiom.CEFR ?? "A0"),
+                CEFR = aiIdiom.CEFR ?? "A0",
                 Frequency = aiIdiom.Frequency ?? "medium",
                 Synonyms = aiIdiom.Synonyms ?? new List<string>(),
                 Example = aiIdiom.Example,
@@ -281,7 +284,7 @@ public class SentenceAnalyzer : ISentenceAnalyzer
                 Definition = $"Please refer to the AI analysis above for detailed definition.",
                 PartOfSpeech = "unknown",
                 Pronunciation = $"/{cleanWord}/",
-                DifficultyLevel = EstimateBasicDifficulty(cleanWord),
+                DifficultyLevelNumeric = EstimateBasicDifficultyNumeric(cleanWord),
                 Frequency = "medium",
                 Synonyms = new List<string>(),
                 Example = null,
@@ -301,17 +304,17 @@ public class SentenceAnalyzer : ISentenceAnalyzer
         return $"{word} - 請查看完整分析";
     }
 
-    private string EstimateBasicDifficulty(string word)
+    private int EstimateBasicDifficultyNumeric(string word)
     {
         var a1Words = new[] { "i", "you", "he", "she", "it", "we", "they", "the", "a", "an", "is", "are", "was", "were", "have", "do", "go", "get", "see", "know" };
         var a2Words = new[] { "make", "think", "come", "take", "use", "work", "call", "try", "ask", "need", "feel", "become", "leave", "put", "say", "tell", "turn", "move" };
 
         var lowerWord = word.ToLower();
-        if (a1Words.Contains(lowerWord)) return "A1";
-        if (a2Words.Contains(lowerWord)) return "A2";
-        if (word.Length <= 4) return "A2";
-        if (word.Length <= 6) return "B1";
-        return "B2";
+        if (a1Words.Contains(lowerWord)) return 1; // A1
+        if (a2Words.Contains(lowerWord)) return 2; // A2
+        if (word.Length <= 4) return 2; // A2
+        if (word.Length <= 6) return 3; // B1
+        return 4; // B2
     }
 }
 
@@ -340,7 +343,7 @@ internal class AiVocabularyAnalysis
     public string? Definition { get; set; }
     public string? PartOfSpeech { get; set; }
     public string? Pronunciation { get; set; }
-    public string? DifficultyLevel { get; set; }
+    public string? CEFR { get; set; }
     public string? Frequency { get; set; }
     public List<string>? Synonyms { get; set; }
     public string? Example { get; set; }
@@ -353,7 +356,7 @@ internal class AiIdiom
     public string? Translation { get; set; }
     public string? Definition { get; set; }
     public string? Pronunciation { get; set; }
-    public string? DifficultyLevel { get; set; }
+    public string? CEFR { get; set; }
     public string? Frequency { get; set; }
     public List<string>? Synonyms { get; set; }
     public string? Example { get; set; }
diff --git a/backend/DramaLing.Api/Services/Vocabulary/Options/OptionsVocabularyService.cs b/backend/DramaLing.Api/Services/Vocabulary/Options/OptionsVocabularyService.cs
index 455e566..917318b 100644
--- a/backend/DramaLing.Api/Services/Vocabulary/Options/OptionsVocabularyService.cs
+++ b/backend/DramaLing.Api/Services/Vocabulary/Options/OptionsVocabularyService.cs
@@ -188,4 +188,20 @@ public class OptionsVocabularyService : IOptionsVocabularyService
 
         return allowed;
     }
+
+    /// <summary>
+    /// 獲取允許的 CEFR 數字等級（包含相鄰等級）
+    /// </summary>
+    private static List<int> GetAllowedCEFRLevelsNumeric(int targetLevelNumeric)
+    {
+        var allowed = new List<int> { targetLevelNumeric };
+
+        // 加入相鄰等級（允許難度稍有差異）
+        if (targetLevelNumeric > 1)
+            allowed.Add(targetLevelNumeric - 1);
+        if (targetLevelNumeric < 6)
+            allowed.Add(targetLevelNumeric + 1);
+
+        return allowed;
+    }
 }
\ No newline at end of file
diff --git a/backend/DramaLing.Api/Utils/CEFRHelper.cs b/backend/DramaLing.Api/Utils/CEFRHelper.cs
new file mode 100644
index 0000000..e1b5fa8
--- /dev/null
+++ b/backend/DramaLing.Api/Utils/CEFRHelper.cs
@@ -0,0 +1,166 @@
+using System.Collections.Generic;
+using System.Linq;
+
+namespace DramaLing.Api.Utils
+{
+    /// <summary>
+    /// CEFR 等級轉換和比較輔助類別
+    /// 處理字串格式 (A1, A2, B1, B2, C1, C2) 與數字格式 (0-6) 的轉換
+    /// </summary>
+    public static class CEFRHelper
+    {
+        /// <summary>
+        /// CEFR 等級映射表
+        /// 0 = 未知/完全沒概念
+        /// 1-6 = A1 到 C2
+        /// </summary>
+        private static readonly Dictionary<string, int> LevelToNumericMap = new()
+        {
+            ["A0"] = 0,
+            ["A1"] = 1,
+            ["A2"] = 2,
+            ["B1"] = 3,
+            ["B2"] = 4,
+            ["C1"] = 5,
+            ["C2"] = 6
+        };
+
+        /// <summary>
+        /// 數字到字串的反向映射
+        /// </summary>
+        private static readonly Dictionary<int, string> NumericToLevelMap =
+            LevelToNumericMap.ToDictionary(kvp => kvp.Value, kvp => kvp.Key);
+
+        /// <summary>
+        /// 將 CEFR 字串等級轉換為數字
+        /// </summary>
+        /// <param name="level">CEFR 等級字串 (A1, A2, B1, B2, C1, C2)</param>
+        /// <returns>數字等級 (0=未知, 1-6=A1-C2)</returns>
+        public static int ToNumeric(string? level)
+        {
+            if (string.IsNullOrWhiteSpace(level))
+                return 0;
+
+            var normalizedLevel = level.Trim().ToUpper();
+            return LevelToNumericMap.TryGetValue(normalizedLevel, out var numeric) ? numeric : 0;
+        }
+
+        /// <summary>
+        /// 將數字等級轉換為 CEFR 字串
+        /// </summary>
+        /// <param name="level">數字等級 (0-6)</param>
+        /// <returns>CEFR 等級字串，無效值返回 "Unknown"</returns>
+        public static string ToString(int level)
+        {
+            return NumericToLevelMap.TryGetValue(level, out var cefr) ? cefr : "Unknown";
+        }
+
+        /// <summary>
+        /// 比較兩個等級：level1 是否高於 level2
+        /// </summary>
+        /// <param name="level1">等級1 (數字)</param>
+        /// <param name="level2">等級2 (數字)</param>
+        /// <returns>level1 > level2</returns>
+        public static bool IsHigherThan(int level1, int level2)
+        {
+            return level1 > level2;
+        }
+
+        /// <summary>
+        /// 比較兩個等級：level1 是否低於 level2
+        /// </summary>
+        /// <param name="level1">等級1 (數字)</param>
+        /// <param name="level2">等級2 (數字)</param>
+        /// <returns>level1 < level2</returns>
+        public static bool IsLowerThan(int level1, int level2)
+        {
+            return level1 < level2;
+        }
+
+        /// <summary>
+        /// 比較兩個等級是否相同
+        /// </summary>
+        /// <param name="level1">等級1 (數字)</param>
+        /// <param name="level2">等級2 (數字)</param>
+        /// <returns>level1 == level2</returns>
+        public static bool IsSameLevel(int level1, int level2)
+        {
+            return level1 == level2;
+        }
+
+        /// <summary>
+        /// 字串版本：比較兩個 CEFR 等級
+        /// </summary>
+        /// <param name="level1">等級1 (字串)</param>
+        /// <param name="level2">等級2 (字串)</param>
+        /// <returns>level1 > level2</returns>
+        public static bool IsHigherThan(string? level1, string? level2)
+        {
+            return IsHigherThan(ToNumeric(level1), ToNumeric(level2));
+        }
+
+        /// <summary>
+        /// 字串版本：比較兩個 CEFR 等級
+        /// </summary>
+        /// <param name="level1">等級1 (字串)</param>
+        /// <param name="level2">等級2 (字串)</param>
+        /// <returns>level1 < level2</returns>
+        public static bool IsLowerThan(string? level1, string? level2)
+        {
+            return IsLowerThan(ToNumeric(level1), ToNumeric(level2));
+        }
+
+        /// <summary>
+        /// 字串版本：比較兩個 CEFR 等級是否相同
+        /// </summary>
+        /// <param name="level1">等級1 (字串)</param>
+        /// <param name="level2">等級2 (字串)</param>
+        /// <returns>level1 == level2</returns>
+        public static bool IsSameLevel(string? level1, string? level2)
+        {
+            return IsSameLevel(ToNumeric(level1), ToNumeric(level2));
+        }
+
+        /// <summary>
+        /// 驗證數字等級是否有效
+        /// </summary>
+        /// <param name="level">數字等級</param>
+        /// <returns>是否在 0-6 範圍內</returns>
+        public static bool IsValidNumericLevel(int level)
+        {
+            return level >= 0 && level <= 6;
+        }
+
+        /// <summary>
+        /// 驗證字串等級是否有效
+        /// </summary>
+        /// <param name="level">字串等級</param>
+        /// <returns>是否為有效的 CEFR 等級</returns>
+        public static bool IsValidStringLevel(string? level)
+        {
+            if (string.IsNullOrWhiteSpace(level))
+                return false;
+
+            var normalizedLevel = level.Trim().ToUpper();
+            return LevelToNumericMap.ContainsKey(normalizedLevel);
+        }
+
+        /// <summary>
+        /// 取得所有有效的數字等級
+        /// </summary>
+        /// <returns>數字等級陣列 (0-6)</returns>
+        public static int[] GetAllNumericLevels()
+        {
+            return new int[] { 0, 1, 2, 3, 4, 5, 6 };
+        }
+
+        /// <summary>
+        /// 取得所有有效的字串等級
+        /// </summary>
+        /// <returns>CEFR 等級字串陣列</returns>
+        public static string[] GetAllStringLevels()
+        {
+            return new string[] { "A1", "A2", "B1", "B2", "C1", "C2" };
+        }
+    }
+}
\ No newline at end of file