fix: 物流签收检查异常后未rollback导致PendingRollbackError

check_delivery_by_tracking 内部捕获 SQLAlchemyError 后仅打日志，未调用 session.rollback()，导致 session 处于 invalid 状态，外层 scheduler 的 session.commit() 触发 PendingRollbackError。

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/logistics_service.py

@@ -1670,10 +1670,13 @@ class LogisticsService:
                             break
                 except Exception as e:
                     logger.warning("[物流签收检查] 订单 %s (单号: %s) 检查失败: %s", order.order_no, order.tracking_number or "未填写", e)
+                    if isinstance(e, SQLAlchemyError):
+                        session.rollback()
                     continue
 
         except SQLAlchemyError as e:
             logger.error("检查物流状态数据库异常: %s", e)
+            session.rollback()
 
     def _update_order_to_delivered(self, session: Session, order) -> None:
         """将订单状态更新为已送达，并同步相关数据。