fix(celery): 修复AsyncResult缺少celery_app导致DisabledBackend错误

- project.py中AsyncResult调用添加app=celery_app参数
- 解决自动分类状态查询时500错误

backend/app/api/v1/project.py

@@ -115,7 +115,8 @@ def project_auto_classify(
         if background:
             # Check if already running
             if project.celery_task_id:
-                existing = AsyncResult(project.celery_task_id)
+                from app.tasks.worker import celery_app
+                existing = AsyncResult(project.celery_task_id, app=celery_app)
                 if existing.state in ("PENDING", "PROGRESS", "STARTED"):
                     return ResponseModel(data={"task_id": project.celery_task_id, "status": existing.state})
 
@@ -163,7 +164,8 @@ def project_auto_classify_status(
         progress = json.loads(project.scan_progress) if project.scan_progress else None
         return ResponseModel(data={"status": project.status, "progress": progress})
 
-    result = AsyncResult(task_id)
+    from app.tasks.worker import celery_app
+    result = AsyncResult(task_id, app=celery_app)
     progress = None
     if result.state == "PROGRESS" and result.info:
         progress = result.info