Fix dynamic production backend URL resolution

frontend/src/App.jsx

@@ -14,7 +14,9 @@ import DashboardCharts from './components/DashboardCharts';
 import TransactionTable from './components/TransactionTable';
 import ManualQueryForm from './components/ManualQueryForm';
 
-const BACKEND_URL = 'http://127.0.0.1:8000';
+const BACKEND_URL = window.location.hostname === 'localhost' || window.location.hostname === '127.0.0.1'
+  ? 'http://127.0.0.1:8000'
+  : window.location.origin;
 
 export default function App() {
   const [modelName, setModelName] = useState('voting');