fix(security): complete security and delivery compliance remediation

backend/app/tasks/alert_tasks.py

@@ -1,5 +1,4 @@
 """告警相关 Celery 任务"""
-import traceback
 from datetime import datetime
 from sqlalchemy import func, case
 from app.core.celery_app import celery_app
@@ -77,6 +76,6 @@ def check_school_offline_alerts():
         send_wechat_markdown(content)
         return {"alerted": True, "schools": len(rows)}
     except Exception as e:
-        return {"alerted": False, "error": str(e), "traceback": traceback.format_exc()}
+        return {"alerted": False, "error": "告警任务失败", "error_type": type(e).__name__}
     finally:
         db.close()