fix(livekit): single UDP media port + pin node_ip for the NAT'd server

The prod box is behind NAT (private 192.168.88.61 behind public 118.95.33.89), so
LiveKit auto-IP-detection would pick the wrong (outbound) address. Pin
rtc.node_ip=118.95.33.89 and collapse media to one UDP port (50000) + TCP 7881 to
minimize the upstream gateway port-forward the network team must add. Docs updated
with the exact forward table.

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

docker-compose.yml

@@ -43,8 +43,8 @@ services:
     volumes:
       - ./livekit.yaml:/etc/livekit.yaml:ro
     ports:
-      - "7881:7881"                    # WebRTC over TCP (fallback)
-      - "50000-50100:50000-50100/udp"  # WebRTC media (UDP) — must match livekit.yaml port range
+      - "7881:7881"          # WebRTC over TCP (fallback)
+      - "50000:50000/udp"    # single WebRTC media UDP port (must match livekit.yaml rtc.udp_port)
     networks:
       - npm