紧急修复: receive_task语法错误 — raise HTTPException括号未闭合导致后端启动失败

backend/app/services/task_service.py

@@ -248,6 +248,9 @@ async def receive_task(
     # 校验：只有 PENDING 状态可接收
     if task.status != TASK_STATUS_PENDING:
         raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=f"只有待接收(PENDING)状态的任务可接收，当前状态: {task.status}",
+        )
 
     now = get_beijing_time()
     task.status = TASK_STATUS_WIP