refactor(comment): unify status transitions with atomic count maintenance

Consolidate comment status changes through transitionStatus() to ensure
posts.comments_count and comments.replies_count are atomically maintained
within the same transaction, preventing inconsistencies between displayed
and stored counts.

- Remove separate ApplyPublishedStats() calls, now handled in UpdateModerationStatus
- Add cache invalidation for admin moderation operations
- Update report auto-hide to use unified status transition

internal/service/report_service.go

@@ -188,7 +188,11 @@ func (s *reportServiceImpl) validateTargetExists(ctx context.Context, targetType
 	return nil
 }
 
-// hideTargetContent 隐藏目标内容
+// hideTargetContent 隐藏目标内容。
+//
+// 评论隐藏统一走 commentRepo.UpdateModerationStatus(published → deleted)，
+// 经由仓储内的统一状态转换层维护 posts.comments_count / comments.replies_count，
+// 避免此前用裸 Update 改 status 导致举报自动隐藏后计数漏减的问题。
 func (s *reportServiceImpl) hideTargetContent(ctx context.Context, targetType model.ReportTargetType, targetID string) error {
 	switch targetType {
 	case model.ReportTargetTypePost:
@@ -205,9 +209,13 @@ func (s *reportServiceImpl) hideTargetContent(ctx context.Context, targetType mo
 		if err != nil {
 			return err
 		}
-		if comment != nil && comment.Status != model.CommentStatusDeleted {
-			comment.Status = model.CommentStatusDeleted
-			return s.commentRepo.Update(comment)
+		// 已是终态（deleted/rejected 等非 published）无需再隐藏，也避免重复调整计数
+		if comment == nil || comment.Status != model.CommentStatusPublished {
+			return nil
+		}
+		// published → deleted：统一状态转换层会原子维护计数（永不为负）
+		if _, err := s.commentRepo.UpdateModerationStatus(targetID, model.CommentStatusDeleted, "举报自动隐藏", "system"); err != nil {
+			return err
 		}
 	case model.ReportTargetTypeMessage:
 		// 消息隐藏通过更新状态实现