fix(frontend): repair merge-damaged syntax left by the pm/RBAC revert cycle

Stray braces in App.tsx / ChangeInventoryPage.tsx, an orphaned admin gate in ArrivalsPage.tsx, and a literal revert commit subject pasted into LoginPage.tsx — all made the committed tree unbuildable.

frontend/src/App.tsx

@@ -101,7 +101,6 @@ function RequireAuth({ children }: { children: React.ReactNode }) {
       return <Navigate to="/panel/pm" replace />;
     }
   }
-  }
   return <>{children}</>;
 }