Remove Lavaplayer and migrate to Lavalink

Replaced the bot's audio handling system by removing Lavaplayer dependencies and migrating to a Lavalink v4 node. Updated `MusicManager`, `TrackScheduler`, and related classes to utilize the `LavalinkClient`. Refactored playlist and track loading logic, task integrations, and event dispatch to integrate with the remote node. Deprecated the custom Udio source, preserving references for a future plugin port. Documented configuration and deployment details for the new audio architecture.

docs/utilities-and-bootstrap.md

@@ -86,7 +86,8 @@ An example configuration file is `bot.properties.example`. Key configuration val
 | `MYSQL_*` | Database connection settings (see [persistence.md](persistence.md)). |
 | `NETNEUTRALITY_SENTRY_DSN` | Enables Sentry when present. |
 | `GITLAB_HOST` / `GITLAB_TOKEN` / `GITLAB_PROJECT_ID` | GitLab issue reporting ([`ReportIssueTask`](tasks.md#worked-example--gitlab-bug-report-modal)). |
-| `NETNEUTRALITY_PO_TOKEN` / `NETNEUTRALITY_VISITOR_DATA` / `NETNEUTRALITY_CIPHER_*` | YouTube playback auth/cipher settings for the [music](music.md) source. |
+| `NETNEUTRALITY_LAVALINK_URI` / `_PASSWORD` / `_NAME` | Connection settings for the [Lavalink node](music.md#settings). |
+| `NETNEUTRALITY_PO_TOKEN` / `NETNEUTRALITY_VISITOR_DATA` / `NETNEUTRALITY_CIPHER_*` | YouTube auth/cipher settings, consumed by the node via `lavalink/application.yml`. |
 
 ## Utility helpers