Laravel 13 support
- update docs for Laravel 13 and current package compatibility
- improve centrifuge:install for Laravel 9-13 app structures
- fix broadcaster auth token generation to use the authenticated Laravel user id
- normalize Centrifugo transport failures into BroadcastException
- fix CentrifugoInterface container binding
- expand test coverage and clean up PHPUnit warnings
- update GitHub Actions to actions/checkout@v6
- add real Docker-based Centrifugo integration checks
- add fresh-install E2E coverage for Laravel apps
- add real websocket private subscribe E2E using centrifuge-js