fix: use naive UTC datetimes for TIMESTAMP WITHOUT TIME ZONE columns

backend/app/services/sync_service.py

@@ -1,6 +1,6 @@
 """Equipment sync service: import from Rentman, upsert into DB, invalidate cache."""
 import logging
-from datetime import datetime, timezone
+from datetime import datetime
 from typing import Any
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -32,7 +32,7 @@ class SyncService:
         log_entry = SyncLog(
             sync_type="equipment",
             status="running",
-            started_at=datetime.now(timezone.utc),
+            started_at=datetime.utcnow(),
         )
         self.db.add(log_entry)
         await self.db.commit()
@@ -70,7 +70,7 @@ class SyncService:
         log_entry.items_processed = items_processed
         log_entry.items_failed = items_failed
         log_entry.error_message = error_message
-        log_entry.completed_at = datetime.now(timezone.utc)
+        log_entry.completed_at = datetime.utcnow()
         await self.db.commit()
 
         return {