feat(livekit): close the room when a pod is deleted

DELETE /api/pods/:id now also calls closeRoom (RoomServiceClient.deleteRoom)
to end the live LiveKit room and disconnect anyone connected. PodView listens
for RoomEvent.Disconnected and returns the user to the pod list, so a deleted
pod cleanly kicks everyone out instead of stranding them in a dead room.

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

backend/src/livekit/rooms.ts

@@ -14,6 +14,19 @@ function svc(): RoomServiceClient {
   return client;
 }
 
+/**
+ * Close a pod's LiveKit room, disconnecting everyone. Best-effort: a missing/
+ * already-empty room is fine. Called when a pod is deleted.
+ */
+export async function closeRoom(podId: string): Promise<void> {
+  if (!isConfigured()) return;
+  try {
+    await svc().deleteRoom(podId);
+  } catch (e) {
+    console.warn(`[livekit] closeRoom ${podId} failed: ${(e as Error).message}`);
+  }
+}
+
 /**
  * Who is currently connected in each pod's LiveKit room, as display names,
  * keyed by pod id (= room name). Empty rooms are omitted. Returns {} if