fix(frontend): refresh pod list on leave so a deleted pod doesn't linger

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -177,6 +177,7 @@ export default function App() {
     setRoom(null);
     setJoinedPodId(null);
     sessionStorage.removeItem(SESSION_KEY);
+    void refresh(); // re-sync the list (e.g. if the pod was deleted out from under us)
   }
 
   const showReconnecting = restoring || (joinedPodId !== null && joinedPod === null);