resolve all ruff check errors

auth/google_auth.py

@@ -555,7 +555,7 @@ def get_credentials(
     # Check for single-user mode
     if os.getenv("MCP_SINGLE_USER_MODE") == "1":
         logger.info(
-            f"[get_credentials] Single-user mode: bypassing session mapping, finding any credentials"
+            "[get_credentials] Single-user mode: bypassing session mapping, finding any credentials"
         )
         credentials = _find_any_credentials(credentials_base_dir)
         if not credentials:

auth/oauth_callback_server.py

@@ -172,7 +172,7 @@ class MinimalOAuthServer:
                 self.server_thread.join(timeout=3.0)
 
             self.is_running = False
-            logger.info(f"Minimal OAuth server stopped")
+            logger.info("Minimal OAuth server stopped")
 
         except Exception as e:
             logger.error(f"Error stopping minimal OAuth server: {e}", exc_info=True)

auth/service_decorator.py

@@ -6,10 +6,6 @@ from datetime import datetime, timedelta
 
 from google.auth.exceptions import RefreshError
 from auth.google_auth import get_authenticated_google_service, GoogleAuthenticationError
-
-logger = logging.getLogger(__name__)
-
-# Import scope constants
 from auth.scopes import (
     GMAIL_READONLY_SCOPE, GMAIL_SEND_SCOPE, GMAIL_COMPOSE_SCOPE, GMAIL_MODIFY_SCOPE, GMAIL_LABELS_SCOPE,
     DRIVE_READONLY_SCOPE, DRIVE_FILE_SCOPE,
@@ -22,6 +18,8 @@ from auth.scopes import (
     TASKS_SCOPE, TASKS_READONLY_SCOPE
 )
 
+logger = logging.getLogger(__name__)
+
 # Service configuration mapping
 SERVICE_CONFIGS = {
     "gmail": {"service": "gmail", "version": "v1"},
@@ -391,7 +389,6 @@ def clear_service_cache(user_email: Optional[str] = None) -> int:
 
 def get_cache_stats() -> Dict[str, Any]:
     """Get service cache statistics."""
-    now = datetime.now()
     valid_entries = 0
     expired_entries = 0