feat: media player API, web player panel, and Hope music MCP

- web/media_server.py: FastAPI service owning the permanent library
  (library.json + ./media volume), yt-dlp YouTube Music search, queued
  download jobs with mp3 transcode (ffmpeg), per-room player desired
  state, and an HTTPS proxy for external live-stream URLs.
- agent/media_mcp.py: Hope tools — search_music, play_song,
  offer_song_choices, pause/resume/stop/skip/seek, now_playing,
  list_library, add_stream.
- agent/agent.py: media toolset wiring + conversation rule (music
  playing disables the agent mic; re-engaging pauses music).
- web UI: slide-out Music panel (search, suggestions, library, live
  stream add, play/pause, ±10s, seek, volume) with a reconciling poller
  and media_state data-channel reports.
- token server returns the minted room name; nginx serves /media/files
  as static (native Range) and proxies /media/api to the media server.
- supervisord runs media-server; compose mounts ./media and adds
  ffmpeg to the image.

supervisord.conf

@@ -56,3 +56,18 @@ environment=
     LIVEKIT_API_SECRET="%(ENV_LIVEKIT_API_SECRET)s",
     VOICE_USERS_FILE="%(ENV_VOICE_USERS_FILE)s",
     VOICE_DEFAULT_USER="%(ENV_VOICE_DEFAULT_USER)s"
+
+[program:media-server]
+; Runs as root because the /data/media bind mount is a host (Unraid) share
+; whose uid does not match the container's voiceuser.
+command=/opt/voice-agent/.venv/bin/python /opt/voice/media_server.py
+user=root
+autostart=true
+autorestart=true
+stdout_logfile=/dev/stdout
+stdout_logfile_maxbytes=0
+redirect_stderr=true
+environment=
+    MEDIA_DIR="%(ENV_MEDIA_DIR)s",
+    MEDIA_SERVER_PORT="%(ENV_MEDIA_SERVER_PORT)s",
+    YTDLP_COOKIES="%(ENV_YTDLP_COOKIES)s"