Fix audio, routing, auth, and stream lifecycle

- Switch OBS output to RTMP; add FFmpeg AAC->Opus transcoding via MediaMTX
  runOnReady so WebRTC can carry audio (WebRTC requires Opus, not AAC)
- Enable RTSP on localhost so FFmpeg reads game path without publisher conflict;
  viewers connect to game-opus path (H264+Opus)
- Fix WHEP/HLS path prefix stripping in NPM advanced config; move all custom
  locations (/whep, /hls, /v3) out of NPM GUI and into advanced conf so
  trailing-slash proxy_pass correctly strips prefixes before hitting MediaMTX
- Fix MediaMTX API port 49997->19997 (49997 was in Windows ephemeral range)
- Add /status proxy endpoint to OBS HTTP server so frontend can poll stream
  readiness without hitting /v3/ through NPM where auth_request blocked it
- Fix authInternalUsers: split publish (localhost only) from read (any IP)
  so WHEP viewers are not challenged with Basic Auth by MediaMTX
- Remove muted attribute from video element; show unmute/play button on
  autoplay block so viewers get audio after one click
- Fix webrtcAdditionalHosts to include LAN IP 192.168.50.254
- Fix hlsAllowOrigin->hlsAllowOrigins deprecation warning
- Move MediaMTX/HTTP server startup to script_load (not streaming started)
  so MediaMTX is ready before OBS attempts RTMP connection
- Log MediaMTX output to bin/mediamtx.log for easier debugging

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

docs/obs-setup.md

@@ -25,7 +25,7 @@ Prerequisites:
    | Frontend HTTP port    | `48080` (default)                                              |
    | Firewall rule name    | `GameStream-UDP-48189` (must match the rule created by install.ps1) |
    | Public URL            | `https://stream.hetherman.cloud`                              |
-   | MediaMTX API URL      | `http://127.0.0.1:49997`                                       |
+   | MediaMTX API URL      | `http://127.0.0.1:19997`                                       |
 
 4. Check the **Script Log** at the bottom - you should see
    `[game_stream] game_stream.py loaded`.
@@ -120,7 +120,7 @@ Should report `False` while not streaming, `True` while streaming.
   (another process is already using them).
 - **Viewers see "Stream offline"** even after you click Start Streaming:
   - Check that the MediaMTX API returns `ready: true`:
-    `curl http://localhost:49997/v3/paths/get/game`
+    `curl http://localhost:19997/v3/paths/get/game`
   - Check OBS's own streaming indicator - if it's red, OBS is not actually
     sending to WHIP. Verify the URL and that the custom service / WHIP
     protocol is selected.