Add Device/Video models, signaling WebSocket, device and content routes

- Prisma: Device model (Quest/Phone, online status, battery, storage,
  game/streaming/cortex state), Video model with likes, VideoLike
- Signaling WebSocket for SDP/ICE relay and device presence
- Device routes: list, status, delete
- Content routes: video CRUD with range-support streaming
- SignalingManager service for device socket registry and heartbeat

src/index.ts

@@ -17,6 +17,7 @@ async function main() {
       process.on(signal, async () => {
         app.log.info(`Received ${signal}, shutting down...`);
         stopTokenRefreshScheduler();
+        (app as any).signalingManager?.cleanup();
         await app.close();
         process.exit(0);
       });