refactor: 移除後端高價值詞彙判定邏輯，完全交由前端處理

❌ 移除的高價值判定方法：
- PostProcessWordAnalysisWithUserLevel (重新判定高價值)
- ExtractHighValueWords (提取高價值詞彙)
- IsHighValueWordDynamic (動態判定高價值)

✅ 簡化analyze-sentence API：
- 移除HighValueWords欄位回應
- 移除高價值重新處理邏輯
- 直接回傳AI原始分析結果

🎯 責任分離：
- 後端：純AI分析、翻譯、語法修正
- 前端：高價值判定基於CEFR等級比較

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/DramaLing.Api/Controllers/AIController.cs

@@ -98,21 +98,19 @@ public class AIController : ControllerBase
                 var finalText = aiAnalysis.GrammarCorrection.HasErrors ?
                     aiAnalysis.GrammarCorrection.CorrectedText : request.InputText;
 
-                // 3. 準備AI分析響應資料（包含個人化資訊）
+                // 3. 準備AI分析響應資料
                 var baseResponseData = new
                 {
                     AnalysisId = Guid.NewGuid(),
                     InputText = request.InputText,
-                    UserLevel = userLevel, // 新增：顯示使用的程度
+                    UserLevel = userLevel,
-                    HighValueCriteria = CEFRLevelService.GetTargetLevelRange(userLevel), // 新增：顯示高價值判定範圍
                     GrammarCorrection = aiAnalysis.GrammarCorrection,
                     SentenceMeaning = new
                     {
                         Translation = aiAnalysis.Translation
                     },
                     FinalAnalysisText = finalText ?? request.InputText,
-                    WordAnalysis = PostProcessWordAnalysisWithUserLevel(aiAnalysis.WordAnalysis, userLevel),
+                    WordAnalysis = aiAnalysis.WordAnalysis,
-                    HighValueWords = ExtractHighValueWords(aiAnalysis.WordAnalysis, userLevel),
                     PhrasesDetected = new object[0] // 暫時簡化
                 };
 
@@ -146,7 +144,6 @@ public class AIController : ControllerBase
                     },
                     FinalAnalysisText = finalText,
                     WordAnalysis = analysis.WordAnalysis,
-                    HighValueWords = analysis.HighValueWords,
                     PhrasesDetected = analysis.PhrasesDetected
                 };
 
@@ -253,7 +250,7 @@ public class AIController : ControllerBase
                     Translation = card.Translation,
                     Explanation = card.Definition, // 使用 AI 生成的定義作為解釋
                     WordAnalysis = GenerateWordAnalysisForSentence(text),
-                    HighValueWords = GetHighValueWordsForSentence(text),
+                    HighValueWords = new string[0], // 移除高價值詞彙判定，由前端負責
                     PhrasesDetected = new[]
                     {
                         new
@@ -318,7 +315,7 @@ public class AIController : ControllerBase
             Translation = translation,
             Explanation = explanation,
             WordAnalysis = GenerateWordAnalysisForSentence(text),
-            HighValueWords = GetHighValueWordsForSentence(text),
+            HighValueWords = new string[0], // 移除高價值詞彙判定，由前端負責
             PhrasesDetected = new[]
             {
                 new
@@ -480,8 +477,6 @@ public class AIController : ControllerBase
             var cleanWord = word.Trim();
             if (string.IsNullOrEmpty(cleanWord) || cleanWord.Length < 2) continue;
 
-            // 判斷是否為高價值詞彙
-            var isHighValue = IsHighValueWordDynamic(cleanWord);
             var difficulty = GetWordDifficulty(cleanWord);
 
             analysis[cleanWord] = new
@@ -494,10 +489,7 @@ public class AIController : ControllerBase
                 synonyms = GetSynonyms(cleanWord),
                 antonyms = new string[0],
                 isPhrase = false,
-                isHighValue = isHighValue,
+                difficultyLevel = difficulty
-                learningPriority = isHighValue ? "high" : "low",
-                difficultyLevel = difficulty,
-                costIncurred = isHighValue ? 0 : 1
             };
         }
 
@@ -510,29 +502,9 @@ public class AIController : ControllerBase
     private string[] GetHighValueWordsForSentence(string text)
     {
         var words = text.ToLower().Split(new[] { ' ', '.', ',', '!', '?' }, StringSplitOptions.RemoveEmptyEntries);
-        return words.Where(w => IsHighValueWordDynamic(w.Trim())).ToArray();
+        return new string[0]; // 移除高價值詞彙判定，由前端負責
     }
 
-    /// <summary>
-    /// 動態判斷高價值詞彙
-    /// </summary>
-    private bool IsHighValueWordDynamic(string word)
-    {
-        // B1+ 詞彙或特殊概念詞彙視為高價值
-        var highValueWords = new[]
-        {
-            "animals", "instincts", "safe", "food", "find",
-            "brought", "meeting", "agreed", "thing",
-            "study", "learn", "important", "necessary",
-            "beautiful", "wonderful", "amazing",
-            "problem", "solution", "different", "special",
-            "cut", "slack", "job", "new", "think", "should",
-            "ashamed", "mistake", "apologized", "felt",
-            "strong", "wind", "knocked", "tree", "park"
-        };
-
-        return highValueWords.Contains(word.ToLower());
-    }
 
     /// <summary>
     /// 獲取詞彙翻譯
@@ -689,73 +661,7 @@ public class AIController : ControllerBase
         };
     }
 
-    /// <summary>
-    /// 後處理詞彙分析，根據用戶程度重新判定重點學習詞彙
-    /// </summary>
-    private Dictionary<string, object> PostProcessWordAnalysisWithUserLevel(
-        Dictionary<string, WordAnalysisResult> originalAnalysis, string userLevel)
-    {
-        var processedAnalysis = new Dictionary<string, object>();
 
-        foreach (var wordPair in originalAnalysis)
-        {
-            var wordData = wordPair.Value;
-
-            // 從AI分析結果取得詞彙難度等級
-            string wordLevel = wordData.DifficultyLevel ?? "A2";
-
-            // 使用CEFRLevelService重新判定是否為重點學習詞彙
-            bool isHighValue = CEFRLevelService.IsHighValueForUser(wordLevel, userLevel);
-
-            // 檢查AI例句
-            _logger.LogInformation("🔍 詞彙 {Word}: AI例句={Example}, AI翻譯={ExampleTranslation}",
-                wordPair.Key, wordData.Example ?? "null", wordData.ExampleTranslation ?? "null");
-
-            // 保留AI分析的其他資料，只重新設定isHighValue
-            processedAnalysis[wordPair.Key] = new
-            {
-                word = wordData.Word ?? wordPair.Key,
-                translation = wordData.Translation ?? "",
-                definition = wordData.Definition ?? "",
-                partOfSpeech = wordData.PartOfSpeech ?? "noun",
-                pronunciation = wordData.Pronunciation ?? $"/{wordPair.Key}/",
-                isHighValue = isHighValue, // 重新判定
-                difficultyLevel = wordLevel,
-                synonyms = GetSynonyms(wordPair.Key), // 補充同義詞
-                example = !string.IsNullOrEmpty(wordData.Example) ?
-                    wordData.Example :
-                    GetQualityExampleSentence(wordPair.Key), // 優先使用AI例句
-                exampleTranslation = !string.IsNullOrEmpty(wordData.ExampleTranslation) ?
-                    wordData.ExampleTranslation :
-                    GetQualityExampleTranslation(wordPair.Key) // 優先使用AI翻譯
-            };
-        }
-
-        return processedAnalysis;
-    }
-
-    /// <summary>
-    /// 從詞彙分析中提取重點學習詞彙
-    /// </summary>
-    private string[] ExtractHighValueWords(Dictionary<string, WordAnalysisResult> wordAnalysis, string userLevel)
-    {
-        var highValueWords = new List<string>();
-
-        foreach (var wordPair in wordAnalysis)
-        {
-            var wordData = wordPair.Value;
-
-            string wordLevel = wordData.DifficultyLevel ?? "A2";
-
-            // 使用CEFRLevelService判定
-            if (CEFRLevelService.IsHighValueForUser(wordLevel, userLevel))
-            {
-                highValueWords.Add(wordPair.Key);
-            }
-        }
-
-        return highValueWords.ToArray();
-    }
 
     /// <summary>
     /// 取得有學習價值的例句