chore(compose): gate livekit behind 'sfu' profile so it stays dormant until enabled

A normal deploy no longer starts the livekit container (it would crashloop with
empty keys before provisioning). Enable with 'docker compose --profile sfu up -d'.

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

docker-compose.yml

@@ -33,6 +33,9 @@ services:
     image: livekit/livekit-server:v1.7
     container_name: bizgaze-livekit
     restart: unless-stopped
+    # Dormant by default: a normal `docker compose up -d` / deploy.sh does NOT start it. Enable SFU
+    # explicitly with `docker compose --profile sfu up -d` after setting the LIVEKIT_* vars (see DEPLOY.md).
+    profiles: ["sfu"]
     command: --config /etc/livekit.yaml
     environment:
       # key: secret, sourced from the same .env as the app so both sign/verify with the same secret.