refactor: Centralize API base URL and clean up

Replaces hardcoded Google API base URLs with `settings.BASE_URL` for improved configurability and maintainability across services.

Removes unused imports and variables from various modules to reduce code bloat and enhance readability.

app/database/initialization.py

@@ -7,7 +7,7 @@ from sqlalchemy import inspect
 from sqlalchemy.orm import Session
 
 from app.database.connection import engine, Base
-from app.database.models import Settings, FileRecord
+from app.database.models import Settings
 from app.log.logger import get_database_logger
 
 logger = get_database_logger()

app/database/services.py

@@ -2,7 +2,7 @@
 数据库服务模块
 """
 from typing import List, Optional, Dict, Any, Union
-from datetime import datetime, timedelta, timezone
+from datetime import datetime, timezone
 from sqlalchemy import func, desc, asc, select, insert, update, delete
 import json
 from app.database.connection import database