add: system plugins

[1Lucas1apk]

Changes

Added the new plugin system and the PluginManager. Plugins can now register custom REST routes, WebSocket interceptors, audio interceptors, middleware, filters, sources and player interceptors. Updated /info to expose plugin metadata. Implemented a working Cloudflare Tunnel plugin and a sample plugin for demonstration. Adjusted the server bootstrap to load plugins in master and worker contexts.

Why

This feature makes NodeLink extensible without modifying core files. It enables developers to integrate new behavior cleanly and encourages future contributions. The design keeps compatibility with existing clients while allowing third-party plugins to hook into core events in a controlled way.

Checkmarks

• The modified endpoints have been tested.
• Used the same indentation as the rest of the project.
• Still compatible with LavaLink clients.

Additional information

The plugin API was designed to be minimal at first but flexible enough for future features, including additional hooks, plugin configuration and validation. The sample plugin serves as practical documentation until formal docs are released.