setup the ci

[hamoda-dev]

• Set up GitHub Actions CI pipeline running across PHP 8.2, 8.3, 8.4, and 8.5
• Add PHPCS (squizlabs/php_codesniffer v4) with PSR-12 coding standard config
• Add PHPStan (v2) static analysis configured at level 1
• Add composer scripts (cs-check, cs-fix, stan, test, check) for easy local execution
• Add CONTRIBUTING.md with setup instructions and available scripts documentation

Test plan

• Run composer install to verify dependencies resolve
• Run composer cs-check to verify PHPCS is wired up
• Run composer stan to verify PHPStan runs at level 1
• Push to branch and confirm GitHub Actions workflow triggers across all PHP versions
• Fix existing violations and uncomment the check steps in CI before merge