feat(subscription): 订阅过期状态自动更新与服务端排序

- 新增 SubscriptionExpiryService 定时任务，每分钟更新过期订阅状态
- 订阅列表支持服务端排序（按过期时间、状态、创建时间）
- 实时显示正确的过期状态，无需等待定时任务
- 允许对已过期订阅进行续期操作
- DataTable 组件支持 serverSideSort 模式

backend/internal/service/subscription_service.go

@@ -330,12 +330,10 @@ func (s *SubscriptionService) ExtendSubscription(ctx context.Context, subscripti
 		newExpiresAt = MaxExpiresAt
 	}
 
-	// 如果是缩短（负数），检查新的过期时间必须大于当前时间
-	if days < 0 {
-		now := time.Now()
-		if !newExpiresAt.After(now) {
-			return nil, ErrAdjustWouldExpire
-		}
+	// 检查新的过期时间必须大于当前时间
+	now := time.Now()
+	if !newExpiresAt.After(now) {
+		return nil, ErrAdjustWouldExpire
 	}
 
 	if err := s.userSubRepo.ExtendExpiry(ctx, subscriptionID, newExpiresAt); err != nil {
@@ -383,6 +381,7 @@ func (s *SubscriptionService) ListUserSubscriptions(ctx context.Context, userID
 		return nil, err
 	}
 	normalizeExpiredWindows(subs)
+	normalizeSubscriptionStatus(subs)
 	return subs, nil
 }
 
@@ -404,17 +403,19 @@ func (s *SubscriptionService) ListGroupSubscriptions(ctx context.Context, groupI
 		return nil, nil, err
 	}
 	normalizeExpiredWindows(subs)
+	normalizeSubscriptionStatus(subs)
 	return subs, pag, nil
 }
 
-// List 获取所有订阅（分页，支持筛选）
-func (s *SubscriptionService) List(ctx context.Context, page, pageSize int, userID, groupID *int64, status string) ([]UserSubscription, *pagination.PaginationResult, error) {
+// List 获取所有订阅（分页，支持筛选和排序）
+func (s *SubscriptionService) List(ctx context.Context, page, pageSize int, userID, groupID *int64, status, sortBy, sortOrder string) ([]UserSubscription, *pagination.PaginationResult, error) {
 	params := pagination.PaginationParams{Page: page, PageSize: pageSize}
-	subs, pag, err := s.userSubRepo.List(ctx, params, userID, groupID, status)
+	subs, pag, err := s.userSubRepo.List(ctx, params, userID, groupID, status, sortBy, sortOrder)
 	if err != nil {
 		return nil, nil, err
 	}
 	normalizeExpiredWindows(subs)
+	normalizeSubscriptionStatus(subs)
 	return subs, pag, nil
 }
 
@@ -441,6 +442,18 @@ func normalizeExpiredWindows(subs []UserSubscription) {
 	}
 }
 
+// normalizeSubscriptionStatus 根据实际过期时间修正状态（仅影响返回数据，不影响数据库）
+// 这确保前端显示正确的状态，即使定时任务尚未更新数据库
+func normalizeSubscriptionStatus(subs []UserSubscription) {
+	now := time.Now()
+	for i := range subs {
+		sub := &subs[i]
+		if sub.Status == SubscriptionStatusActive && !sub.ExpiresAt.After(now) {
+			sub.Status = SubscriptionStatusExpired
+		}
+	}
+}
+
 // startOfDay 返回给定时间所在日期的零点（保持原时区）
 func startOfDay(t time.Time) time.Time {
 	return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
@@ -659,11 +672,6 @@ func (s *SubscriptionService) GetUserSubscriptionsWithProgress(ctx context.Conte
 	return progresses, nil
 }
 
-// UpdateExpiredSubscriptions 更新过期订阅状态（定时任务调用）
-func (s *SubscriptionService) UpdateExpiredSubscriptions(ctx context.Context) (int64, error) {
-	return s.userSubRepo.BatchUpdateExpiredStatus(ctx)
-}
-
 // ValidateSubscription 验证订阅是否有效
 func (s *SubscriptionService) ValidateSubscription(ctx context.Context, sub *UserSubscription) error {
 	if sub.Status == SubscriptionStatusExpired {