Adds the server side of scaling meetings past the ~5-peer mesh:
- config.js: LIVEKIT_URL/API_KEY/API_SECRET + LIVEKIT_ENABLED flag. All optional;
when unset the app keeps the built-in P2P mesh (fully additive, like push).
- routes.js: GET /api/meetings/config (tells the client sfu on/off + wss url) and
POST /api/meetings/token (mints a per-user, per-room LiveKit join token — hand-rolled
HS256 JWT like the FCM/APNs tokens, no new dependency; secret stays server-side).
- docker-compose.yml: optional livekit service (single-node, no Redis), keys injected
via LIVEKIT_KEYS from the same .env; media over published UDP 50000-50100 + TCP 7881,
signaling proxied by NPM.
- livekit.yaml + .env.example documented.
Client (mesh->LiveKit media swap, behind the flag) lands in phase 2.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
