fix: submit_waybills 缩进错误导致后端无法启动

def submit_waybills 被错误缩进到 recognize_waybill 方法内部，
恢复到正确的类级别缩进。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/app/services/logistics_service.py

@@ -751,7 +751,7 @@ class LogisticsService:
             "raw_result": raw_result,
         }
 
-        def submit_waybills(self, task_id: int, payload: dict, session: Session | None = None, current_user: dict | None = None) -> dict:
+    def submit_waybills(self, task_id: int, payload: dict, session: Session | None = None, current_user: dict | None = None) -> dict:
         """批量提交运单号，校验任务状态。"""
         if session is None:
             raise AppException(code=ErrorCode.INTERNAL_ERROR, message="数据库连接不可用", status_code=500)