**Add autoplay support for seamless music playback**

Introduced autoplay functionality to keep music playing when the queue ends. Added new `/autoplay` API endpoints, command handling, and service implementations. Enhanced `TrackScheduler`, queue operations, and testing to support autoplay behavior. Integrated YouTube radio mix as the initial provider.

docs/commands.md

@@ -147,6 +147,7 @@ Concrete commands live under `me.bobert.netneutrality.command.*`, grouped by fea
 | `JoinCommand` / `LeaveCommand` | `music` | Slash | Join / leave the voice channel. |
 | `CurrentlyPlayingCommand` | `music` | Slash | Show the currently playing track. |
 | `ResumeCommand` / `StopCommand` / `VolumeCommand` | `music` | Slash | Playback controls. |
+| `AutoplayCommand` | `music` | Slash | Toggle autoplay: queues the YouTube radio mix of the last track so music keeps playing. |
 | `BitconnectCommand` | `music` | Slash | Novelty music command. |
 | `CreateEmojiReaction` / `ModifyEmojiReaction` | `react` | Message menu | Create/modify emoji-role mappings from a message. |
 | `DatabaseCommand`, `PurgeCommand`, `ShutdownCommand`, `JoinClanCommand`, `TestCommand`, `SlashCommandTest`, `TrackStuckTest` | `custom` | Mixed | Owner/debug and personal utilities (the `custom` package is gitignored per-deployment). |

docs/music.md

@@ -166,5 +166,5 @@ scope of this migration and is tracked as a follow-up.
 All music commands extend [`MusicCommand`](commands.md#base-implementations-corecommandimpl) (guild
 only + music role/channel enforced): `PlayCommand`, `SkipCommand`/`VoteSkipCommand`,
 `QueueCommand`/`ViewQueueCommand`, `ClearQueueCommand`, `ShuffleCommand`, `JoinCommand`/`LeaveCommand`,
-`CurrentlyPlayingCommand`, `ResumeCommand`/`StopCommand`, `VolumeCommand`, `BitconnectCommand`. See
+`CurrentlyPlayingCommand`, `ResumeCommand`/`StopCommand`, `VolumeCommand`, `AutoplayCommand`, `BitconnectCommand`. See
 [commands.md](commands.md#command-catalog).

docs/web-api.md

@@ -70,6 +70,7 @@ music channel when a context is attached.
 | `PATCH /music/{guildId}/queue/reorder` | Move a track (`fromPosition` → `toPosition`). |
 | `POST /music/{guildId}/skip`, `/stop`, `/pause`, `/resume`, `/shuffle`, `/leave` | Playback controls. |
 | `GET` / `PUT /music/{guildId}/volume` | Read / set volume (0–100). |
+| `GET` / `PUT /music/{guildId}/autoplay` | Read / set autoplay (`{"enabled": true}`). In-memory, resets when the player is destroyed. |
 | `PUT /music/{guildId}/seek` | Seek to `positionMs`. |
 | `GET /music/{guildId}/vote-skip` | Vote-skip status. |
 | `POST /music/{guildId}/vote-skip/{userId}` | Cast a vote on behalf of a member. |