Fix linting issues with ruff --fix

Applied automatic fixes for 315 out of 597 linting errors:
- Remove unused imports (F401)
- Fix f-string without placeholders (F541)
- Split multiple imports (E401)
- Remove redundant import aliases

Remaining 272 errors are mostly style issues:
- 164 E701: Multiple statements on one line (colon)
- 70 E402: Module import not at top of file
- 13 F841: Unused variables
- Various other style warnings

Code functionality unchanged - all fixes are cosmetic improvements.

redis_session_store.py

@@ -11,8 +11,8 @@ import os
 import json
 import time
 import logging
-from typing import Optional, Dict, Any, Union
-from datetime import datetime, timedelta
+from typing import Optional, Dict, Any
+from datetime import datetime
 
 logger = logging.getLogger(__name__)