fix: resolve lint errors in test files [CAR-932]

Fix 56 lint errors in test files that were blocking CI:
- E501: Split long SQL INSERT statements across multiple lines
- F401: Remove unused imports (os, unittest.mock.patch)

Co-Authored-By: Paperclip <noreply@paperclip.ing>

tests/test_middleware/test_rate_limit.py

@@ -1,7 +1,7 @@
 """Tests for rate limiting middleware."""
 
 import time
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import AsyncMock, MagicMock
 
 import pytest