Add music bot for self-hosted Stoat with web control panel

Plays audio into Stoat voice channels over LiveKit and exposes the same
player through both chat commands and a browser panel, so the two never
drift apart: everything routes through a single MusicManager.

- core: per-server GuildPlayer (queue, loop, shuffle, seek, volume,
  idle auto-leave) driving revoice.js/@livekit/rtc-node and ffmpeg
- sources: yt-dlp for YouTube/SoundCloud, direct media URLs and internet
  radio, optional local library with path-traversal guards
- bot: 18 chat commands with aliases, plus !panel one-time login links
- api: Fastify REST + WebSocket, sessions authenticated against the
  instance's own /auth/session/login (TOTP supported), permissions
  re-checked against Stoat membership and roles on every request
- web: React panel with search, queue editing, seek and volume
- deploy: Dockerfile, compose.override.yml and Caddyfile snippets for
  dropping the service into an existing /opt/stoat stack

Verified with npm run typecheck, both builds, and scripts/smoke-api.mjs
(9 API checks). Voice playback itself needs a live instance to test.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/src/types.ts

@@ -0,0 +1,54 @@
+export type SourceKind = "youtube" | "soundcloud" | "direct" | "local";
+export type LoopMode = "off" | "track" | "queue";
+export type PlayerStatus = "idle" | "connecting" | "buffering" | "playing" | "paused";
+
+export interface Track {
+  id: string;
+  title: string;
+  author: string | null;
+  duration: number;
+  isLive: boolean;
+  url: string;
+  thumbnail: string | null;
+  source: SourceKind;
+  requestedBy: { id: string; username: string };
+}
+
+export interface PlayerState {
+  serverId: string;
+  serverName: string | null;
+  voiceChannelId: string | null;
+  voiceChannelName: string | null;
+  status: PlayerStatus;
+  current: Track | null;
+  position: number;
+  queue: Track[];
+  history: Track[];
+  volume: number;
+  loop: LoopMode;
+  updatedAt: number;
+}
+
+export interface VoiceChannel {
+  id: string;
+  name: string;
+}
+
+export interface ServerRef {
+  id: string;
+  name: string;
+  iconUrl: string | null;
+}
+
+export interface Me {
+  user: { id: string; username: string };
+  servers: ServerRef[];
+  features: { localLibrary: boolean };
+}
+
+export interface ServerStateResponse {
+  state: PlayerState;
+  voiceChannels: VoiceChannel[];
+  yourVoiceChannel: VoiceChannel | null;
+  canControl: boolean;
+}