fix: 单订阅模式下避免重复创建订阅

1. FindSingleModeAnchorSubscribe 补充 status=4（流量耗完）到查询范围，
   避免流量耗尽的订阅被忽略导致续费时新建订阅

2. activateOrderLogic NewPurchase 路径去掉套餐ID匹配检查，
   单订阅模式下无论购买何种套餐都更新现有订阅而非新建

3. singleModeHelper fallback 查询同步补充 status=4

Co-Authored-By: claude-flow <ruv@ruv.net>

internal/model/user/subscribe.go

@@ -67,7 +67,7 @@ func (m *defaultUserModel) FindSingleModeAnchorSubscribe(ctx context.Context, us
 	var data Subscribe
 	err := m.QueryNoCacheCtx(ctx, &data, func(conn *gorm.DB, _ interface{}) error {
 		return conn.Model(&Subscribe{}).
-			Where("user_id = ? AND token != '' AND (order_id > 0 OR token LIKE 'iap:%') AND `status` IN ?", userId, []int64{0, 1, 2, 3, 5}).
+			Where("user_id = ? AND token != '' AND (order_id > 0 OR token LIKE 'iap:%') AND `status` IN ?", userId, []int64{0, 1, 2, 3, 4, 5}).
 			Order("expire_time DESC").
 			Order("updated_at DESC").
 			Order("id DESC").