feat: 平台同步状态记录（last_synced_at + 前端展示最后同步时间）

app/services/sync_service.py

@@ -6,6 +6,7 @@
 """
 
 import json
+from datetime import datetime
 from typing import Optional
 
 from fastapi import HTTPException, status
@@ -217,4 +218,8 @@ def sync_provider(session: Session, provider_id: int) -> dict:
         except Exception as e:  # noqa: BLE001
             result["account_error"] = str(e)
 
+    provider.last_synced_at = datetime.utcnow()
+    session.add(provider)
+    session.commit()
+    result["last_synced_at"] = provider.last_synced_at.isoformat()
     return result