feat: integrate PHPStan, Rector and Pint code quality tools (#13)

* feat: integrate PHPStan, Rector and Pint code quality tools

- Add larastan, rector, and rector-laravel dev dependencies
- Configure PHPStan at max level with Larastan extension
- Configure Rector with Laravel sets and code quality rules
- Configure Pint with strict rules (final_class, strict_types)
- Add composer scripts: lint, test:lint, test:types, test:unit
- Add GitHub Actions workflow for CI on push/PR
- Apply code style fixes across all files

* docs: add code quality section to README

routes/console.php

@@ -1,8 +1,10 @@
 <?php
 
+declare(strict_types=1);
+
 use Illuminate\Foundation\Inspiring;
 use Illuminate\Support\Facades\Artisan;
 
-Artisan::command('inspire', function () {
+Artisan::command('inspire', function (): void {
     $this->comment(Inspiring::quote());
 })->purpose('Display an inspiring quote');