Integrate LiveKit SFU and harden booking workflow

docker-compose.yml

@@ -53,6 +53,29 @@ services:
     # HEALTHCHECK instruction (GET /api/health, which itself checks Postgres
     # connectivity) — nothing to duplicate here.
 
+  # Self-hosted LiveKit SFU. Host networking is intentional: WebRTC media
+  # needs the UDP port range below to be reachable directly from the internet.
+  livekit:
+    image: livekit/livekit-server:latest
+    restart: unless-stopped
+    network_mode: host
+    env_file:
+      - .env
+    environment:
+      LIVEKIT_CONFIG: |
+        port: 7880
+        log_level: info
+        rtc:
+          tcp_port: 7881
+          port_range_start: 50000
+          port_range_end: 60000
+          use_external_ip: true
+        keys:
+          ${LIVEKIT_API_KEY}: ${LIVEKIT_API_SECRET}
+        turn:
+          enabled: true
+          udp_port: 3478
+
   # Optional external network to a reverse proxy (e.g. Nginx Proxy Manager)
   # is attached via docker-compose.override.yml, generated by setup.sh only
   # when such a network is actually detected — see DEPLOYMENT.md. Nothing