Add explicit fail condition for subuser node key in route permissions

- Ensure permissions pass only if an explicit subuser node key is granted.
- Prevent fallback to classic user permissions in this authentication branch.

services/nginx/app/traits/route_t.php

@@ -375,6 +375,10 @@ trait route_t
                         return true;
                     }
                 }
+                // IMPORTANT: When a subuser is authenticated and a subusers node key is defined
+                // the permission must ONLY pass if the explicit subuser node is granted.
+                // Do NOT fall back to classic user permissions in this branch.
+                return false;
             }
             $user = $auth->get_user();
             if (!$user) {