fix(backend): redact retryable MAX storage failures

Refs #82

tests/test_api_max.py

@@ -1,9 +1,13 @@
 """MAX endpoints authenticate before reading bindings or accepting events."""
 
+import sys
+from types import SimpleNamespace
+from unittest.mock import AsyncMock
 from urllib.parse import parse_qs, urlsplit
 
 import pytest
 from httpx import ASGITransport, AsyncClient
+from sqlalchemy.exc import OperationalError
 
 from app.config import get_settings
 from app.core import clock
@@ -90,3 +94,10 @@ async def test_webhook_secret_checked_before_body_or_adapter(client):
     assert (await client.post(HOOK, headers=headers, content="not-json")).status_code == 400
     assert (await client.post(HOOK, headers=headers, json=[])).status_code == 422
     assert (await client.post(HOOK, headers=headers, content=" " * 65537)).status_code == 413
+
+
+async def test_webhook_storage_failure_is_retryable_without_identity_details(client, monkeypatch):
+    handler = AsyncMock(side_effect=OperationalError("private SQL", {"token": TOKEN}, Exception("private")))
+    monkeypatch.setitem(sys.modules, "app.channels.max_bot", SimpleNamespace(handle_update=handler))
+    response = await client.post(HOOK, headers={"X-Max-Bot-Api-Secret": SECRET}, json={})
+    assert response.status_code == 503 and TOKEN not in response.text and "private" not in response.text