feat: add Laravel 13 support

First tagged release.

- Laravel 12 + 13 support (illuminate/contracts ^12.0||^13.0)
- PHP 8.3 + 8.4
- CI matrix: 4 jobs (PHP 8.3/8.4 × L12/L13)
- spatie/laravel-translatable ^6.13
- orchestra/testbench ^10.0||^11.0