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>

server/reflector/views/rtc_offer.py

@@ -10,6 +10,7 @@ from pydantic import BaseModel
 from reflector.events import subscribers_shutdown
 from reflector.logger import logger
 from reflector.pipelines.runner import PipelineRunner
+from reflector.settings import settings
 
 sessions = []
 router = APIRouter()
@@ -123,7 +124,16 @@ async def rtc_offer_base(
     # update metrics
     m_rtc_sessions.inc()
 
-    return RtcOffer(sdp=pc.localDescription.sdp, type=pc.localDescription.type)
+    sdp = pc.localDescription.sdp
+
+    # Rewrite ICE candidate IPs when running behind Docker bridge networking
+    if settings.WEBRTC_HOST:
+        from reflector.webrtc_ports import resolve_webrtc_host, rewrite_sdp_host
+
+        host_ip = resolve_webrtc_host(settings.WEBRTC_HOST)
+        sdp = rewrite_sdp_host(sdp, host_ip)
+
+    return RtcOffer(sdp=sdp, type=pc.localDescription.type)
 
 
 @subscribers_shutdown.append