feat: add sliding session timeout with idle and absolute caps

gatehouse_app/services/session_service.py

@@ -10,10 +10,10 @@ class SessionService:
     @staticmethod
     def get_active_session_by_token(token):
         """Get active session by token.
-        
+
         Args:
             token: The session token string
-            
+
         Returns:
             Session object if found and active, None otherwise
         """
@@ -23,6 +23,8 @@ class SessionService:
             token=token,
             status=SessionStatus.ACTIVE,
             deleted_at=None
+        ).filter(
+            Session.expires_at > datetime.now(timezone.utc)
         ).first()
 
     @staticmethod