feat(repository): enhance repository methods with batch processing and transaction support

- Updated Like and Unlike methods in CommentRepository to use transactions for data consistency.
- Introduced IsLikedBatch method for batch checking if comments are liked, addressing N+1 query issues.
- Enhanced BatchDelete method in PostRepository to perform batch deletions within a single transaction, improving efficiency.
- Added BatchUpdateStatus method for posts to utilize a single SQL update for status changes, reducing database load.
- Implemented BatchUpdateSortOrder in StickerRepository using CASE WHEN for efficient sorting updates.
- Added IsFollowingBatch and IsBlockedBatch methods in UserRepository for batch checking follow and block relationships, optimizing performance.

internal/repository/sticker_repo.go

@@ -2,6 +2,7 @@ package repository
 
 import (
 	"carrot_bbs/internal/model"
+	"strings"
 
 	"gorm.io/gorm"
 )
@@ -88,18 +89,31 @@ func (r *stickerRepository) UpdateSortOrder(id string, sortOrder int) error {
 		Update("sort_order", sortOrder).Error
 }
 
-// BatchUpdateSortOrder 批量更新排序
+// BatchUpdateSortOrder 批量更新排序（使用 CASE WHEN 批量更新，避免 N+1 问题）
 func (r *stickerRepository) BatchUpdateSortOrder(userID string, orders map[string]int) error {
-	return r.db.Transaction(func(tx *gorm.DB) error {
-		for id, sortOrder := range orders {
-			if err := tx.Model(&model.UserSticker{}).
-				Where("id = ? AND user_id = ?", id, userID).
-				Update("sort_order", sortOrder).Error; err != nil {
-				return err
-			}
-		}
+	if len(orders) == 0 {
 		return nil
-	})
+	}
+
+	// 构建 CASE WHEN 批量更新 SQL
+	var cases []string
+	var args []any
+
+	for id, sortOrder := range orders {
+		cases = append(cases, "WHEN id = ? THEN ?")
+		args = append(args, id, sortOrder)
+	}
+
+	ids := make([]string, 0, len(orders))
+	for id := range orders {
+		ids = append(ids, id)
+	}
+
+	sql := `UPDATE user_stickers SET sort_order = CASE ` + 
+		strings.Join(cases, " ") + ` END WHERE id IN ? AND user_id = ?`
+	args = append(args, ids, userID)
+
+	return r.db.Exec(sql, args...).Error
 }
 
 // CountByUserID 获取用户表情数量