fix: 修复证据上传审计并补充前端操作提示要求

tests/unit/service/test_risk_evidence_archive_service.py

@@ -106,6 +106,7 @@ async def test_archive_success_updates_snapshot_and_audit() -> None:
     assert item.evidence_snapshot["evidence_archive"]["file_size"] == len(PNG)
     assert session.committed is True
     assert session.added[0].action_type == "risk_evidence_archived"
+    assert session.added[0].created_at is not None
 
 
 @pytest.mark.asyncio