fix: 修復所有資料變更操作的快取問題

- 統一所有 CRUD 操作使用 refetch() 而非 refresh()
- 確保新增、刪除、收藏切換後畫面立即更新
- 解決刪除成功但畫面未更新的問題

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

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

frontend/app/flashcards/page.tsx

@@ -171,7 +171,7 @@ function FlashcardsContent() {
     try {
       const result = await flashcardsService.deleteFlashcard(card.id)
       if (result.success) {
-        await searchActions.refresh()
+        await searchActions.refetch()
         await loadTotalCounts()
         toast.success(`詞卡「${card.word}」已刪除`)
       } else {
@@ -186,7 +186,7 @@ function FlashcardsContent() {
     try {
       const result = await flashcardsService.toggleFavorite(card.id)
       if (result.success) {
-        await searchActions.refresh()
+        await searchActions.refetch()
         await loadTotalCounts()
         toast.success(`${card.isFavorite ? '已取消收藏' : '已加入收藏'}「${card.word}」`)
       } else {