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/npm-setup.md

@@ -51,7 +51,7 @@ forward-auth gating).
 |----------|--------|------------------|--------------|
 | `/whep`  | `http` | `<PC-LAN-IP>`    | `48889`       |
 | `/hls`   | `http` | `<PC-LAN-IP>`    | `48888`       |
-| `/v3`    | `http` | `<PC-LAN-IP>`    | `49997`       |
+| `/v3`    | `http` | `<PC-LAN-IP>`    | `19997`       |
 
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