fixes and refactor

test_customers.py

@@ -1,7 +1,7 @@
 """Tests for Customers API using FastAPI TestClient (no live server required)."""
 import os
 import uuid
-from datetime import datetime
+from datetime import datetime, timezone
 
 import pytest
 from fastapi.testclient import TestClient
@@ -88,7 +88,7 @@ def test_customers_crud_and_queries(client: TestClient):
     # Update
     resp = client.put(
         f"/api/customers/{unique_id}",
-        json={"memo": f"Updated at {datetime.utcnow().isoformat()}"},
+        json={"memo": f"Updated at {datetime.now(timezone.utc).isoformat()}"},
     )
     assert resp.status_code == 200