fix: remove unused imports (Request, TestClient, List)

- Remove unused Request and TestClient imports from test_domain_whitelist.py
- Remove unused List import from domain_whitelist.py
- Addresses CodeQL static analysis warnings
- All tests passing

Author: garland3

backend/core/domain_whitelist.py

@@ -8,7 +8,7 @@
 import json
 import logging
 from pathlib import Path
-from typing import List, Optional, Set
+from typing import Optional, Set
 from dataclasses import dataclass
 
 logger = logging.getLogger(__name__)

backend/tests/test_domain_whitelist.py

@@ -4,8 +4,7 @@
 import pytest
 import tempfile
 from pathlib import Path
-from fastapi import FastAPI, Request
-from starlette.testclient import TestClient
+from fastapi import FastAPI
 
 from core.domain_whitelist_middleware import DomainWhitelistMiddleware
 from core.domain_whitelist import DomainWhitelistManager