feat: remove network_mode host for standalone WebRTC (#864)

* feat: remove network_mode host for standalone by fixing WebRTC port range and ICE candidates

aioice hardcodes bind(addr, 0) for ICE UDP sockets, making port mapping
impossible in Docker bridge networking. This adds two env-var-gated
mechanisms to replace network_mode: host:

1. WEBRTC_PORT_RANGE (e.g. "50000-50100"): monkey-patches aioice to bind
   UDP sockets within a known range, so they can be mapped in Docker.

2. WEBRTC_HOST (e.g. "host.docker.internal"): rewrites container-internal
   IPs in SDP answers with the Docker host's real IP, so LAN clients can
   reach the ICE candidates.

Both default to None — no effect on existing deployments.

* fix: do not attempt sidecar to detect host ip, use the standalone script to figure out the external ip and use it

* style: reformat

---------

Co-authored-by: tito <tito@titos-Mac-Studio.local>

docker-compose.standalone.yml

@@ -23,6 +23,7 @@ services:
       context: server
     ports:
       - "1250:1250"
+      - "50000-50100:50000-50100/udp"
     extra_hosts:
       - "host.docker.internal:host-gateway"
     volumes:
@@ -48,6 +49,9 @@ services:
       DIARIZATION_URL: http://cpu:8000
       # Caddy reverse proxy prefix
       ROOT_PATH: /server-api
+      # WebRTC: fixed UDP port range for ICE candidates (mapped above).
+      # WEBRTC_HOST is set by setup-standalone.sh in server/.env (LAN IP detection).
+      WEBRTC_PORT_RANGE: "50000-50100"
     depends_on:
       postgres:
         condition: service_healthy