feat(frontend): scaffold PWA with LiveKit join flow

Vite + React + TS + Tailwind v4, installable PWA. Join-pod UI that fetches a
LiveKit token from the backend, connects to the pod room, and publishes screen
+ mic so PodMan can watch.

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

frontend/src/lib/pod.ts

@@ -0,0 +1,38 @@
+import { Room, RoomEvent } from 'livekit-client';
+
+const BACKEND_URL = import.meta.env.VITE_BACKEND_URL || 'http://localhost:8787';
+
+/** Ask the backend for a LiveKit token to join a pod. */
+export async function fetchPodToken(
+  podId: string,
+  identity: string,
+  name: string,
+): Promise<{ token: string; url: string }> {
+  const res = await fetch(`${BACKEND_URL}/pods/${encodeURIComponent(podId)}/token`, {
+    method: 'POST',
+    headers: { 'content-type': 'application/json' },
+    body: JSON.stringify({ identity, name }),
+  });
+  if (!res.ok) throw new Error(`token request failed: ${res.status}`);
+  return res.json();
+}
+
+/**
+ * Join a pod: connect to the LiveKit room and publish screen + mic so PodMan
+ * can watch. Returns the connected Room.
+ */
+export async function joinPod(podId: string, identity: string, name: string): Promise<Room> {
+  const { token, url } = await fetchPodToken(podId, identity, name);
+  const room = new Room({ adaptiveStream: true, dynacast: true });
+  room.on(RoomEvent.Disconnected, () => console.log('[podman] disconnected'));
+
+  await room.connect(url, token);
+
+  const screen = await navigator.mediaDevices.getDisplayMedia({ video: true });
+  for (const track of screen.getTracks()) {
+    await room.localParticipant.publishTrack(track);
+  }
+  await room.localParticipant.setMicrophoneEnabled(true);
+
+  return room;
+}