Add Laravel 13 Support

[evan-burrell]

Summary

• Add ^13.0 to all illuminate/*, laravel/framework, and orchestra/testbench version constraints
• Add ^8.0 to symfony/http-kernel constraint (Laravel 13 uses Symfony 7.4/8.0)
• Add Laravel 13 (^13.0 and 13.x-dev) to CI test matrix
• Exclude PHP 8.2 from Laravel 13 matrix combinations (Laravel 13 requires PHP 8.3+)
• Add Carbon ^3.0 pin for PHP 8.5 prefer-lowest builds

Test plan

• CI passes for all Laravel 11, 12, and 13 matrix combinations
• PHP 8.2 + Laravel 13 combinations are correctly excluded
• prefer-lowest and prefer-stable both resolve successfully