TURN fixes

Mirror of upstream coop-cloud/lasuite-meet#6:
- fix: resolve TURN_DOMAIN default at .env layer (compose.yml does not
  recursively expand nested ${...} references)
- docs: document host UDP buffer sysctl tuning for LiveKit
- docs: mention Chrome required on mobile
- docs: fix ports table formatting

Upstream: https://git.coopcloud.tech/coop-cloud/lasuite-meet/pulls/6

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

compose.yml

@@ -191,7 +191,7 @@ services:
       - LIVEKIT_NODE_IP
       - LIVEKIT_FORCE_TCP=${LIVEKIT_FORCE_TCP:-false}
       - LIVEKIT_TURN_ENABLED=${LIVEKIT_TURN_ENABLED:-true}
-      - TURN_DOMAIN=${TURN_DOMAIN:-${LIVEKIT_DOMAIN}}
+      - TURN_DOMAIN=${TURN_DOMAIN}
       - TURN_UDP_PORT=${TURN_UDP_PORT:-443}
     # WebRTC ICE ports must be published directly on the host.
     # These carry raw RTP media, not HTTP — cannot be proxied through Traefik without extra traefik compose.