fix: 修正 generate 頁面硬編碼 API URL 問題

- 🔧 修正 app/generate/page.tsx 中的硬編碼端口
- 🔧 修正 useSentenceAnalysis.ts Hook 中的硬編碼端口
- ✅ 統一使用 API_CONFIG.BASE_URL 配置
- ✅ 修正 "Failed to fetch" 錯誤
- ⚙️ 確保 AI 句子分析功能正常運作

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

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

frontend/app/generate/page.tsx

@@ -8,6 +8,7 @@ import { useToast } from '@/components/shared/Toast'
 import { flashcardsService } from '@/lib/services/flashcards'
 import { compareCEFRLevels, getLevelIndex, getTargetLearningRange } from '@/lib/utils/cefrUtils'
 import { BluePlayButton } from '@/components/shared/BluePlayButton'
+import { API_CONFIG } from '@/lib/config/api'
 import Link from 'next/link'
 
 // 常數定義
@@ -51,7 +52,7 @@ function GenerateContent() {
     setIsAnalyzing(true)
 
     try {
-      const response = await fetch('http://localhost:5008/api/ai/analyze-sentence', {
+      const response = await fetch(`${API_CONFIG.BASE_URL}/api/ai/analyze-sentence`, {
         method: 'POST',
         headers: {
           'Content-Type': 'application/json'

frontend/hooks/generate/useSentenceAnalysis.ts

@@ -1,6 +1,7 @@
 import { useState } from 'react'
 import { useToast } from '@/components/shared/Toast'
 import { getLevelIndex } from '@/lib/utils/cefrUtils'
+import { API_CONFIG } from '@/lib/config/api'
 
 interface AnalysisResult {
   originalText: string
@@ -19,7 +20,7 @@ export function useSentenceAnalysis() {
     setIsAnalyzing(true)
 
     try {
-      const response = await fetch('http://localhost:5008/api/ai/analyze-sentence', {
+      const response = await fetch(`${API_CONFIG.BASE_URL}/api/ai/analyze-sentence`, {
         method: 'POST',
         headers: {
           'Content-Type': 'application/json'