refactor: consolidate user and superadmin sessions into unified model

gatehouse_app/decorators/superadmin.py

@@ -15,7 +15,7 @@ def superadmin_required(f):
     """Decorator to require superadmin Bearer token authentication.
     
     Extracts token from Authorization: Bearer {token} header,
-    validates the session against SuperadminSession table,
+    validates the session against the unified sessions table,
     and sets g.current_superadmin and g.superadmin_session.
     
     Returns 401 if no valid session, 403 if not a superadmin.
@@ -46,10 +46,14 @@ def superadmin_required(f):
         token = parts[1]
         
         # Import here to avoid circular imports
-        from gatehouse_app.models.superadmin import SuperadminSession, Superadmin
+        from gatehouse_app.models.user.session import Session
+        from gatehouse_app.models.superadmin import Superadmin
+        from gatehouse_app.utils.constants import SessionType
         
-        # Get active session by token
-        session = SuperadminSession.query.filter_by(token=token).first()
+        # Get active session by token, scoped to superadmin
+        session = Session.query.filter_by(
+            token=token, owner_type=SessionType.SUPERADMIN
+        ).first()
         
         if not session:
             return api_response(
@@ -68,8 +72,8 @@ def superadmin_required(f):
                 error_type="SESSION_INACTIVE"
             )
         
-        # Get the superadmin
-        superadmin = session.superadmin
+        # Get the superadmin by owner_id
+        superadmin = Superadmin.query.get(session.owner_id)
         if not superadmin:
             return api_response(
                 success=False,