Upgrade to PHP 8

[oleche]

Upgrade to PHP 8.4 with PHPUnit Testing and CI/CD

Summary

This PR upgrades the project from PHP 5.5+ to PHP 8.4, adds a comprehensive PHPUnit test suite, Docker-based testing environment, and GitHub Actions CI/CD pipeline.

Changes

Dependencies

• PHP: >=5.5.0 → ^8.4
• vlucas/phpdotenv: 2.4.0 → ^5.6
• phpunit/phpunit: Added ^11.5 as dev dependency

Testing

• Added PHPUnit 11.5 with 30 unit tests covering all source files
• Tests can be run locally via Docker: make test

Docker

• Updated Dockerfile to PHP 8.4
• Added .dockerignore for optimized builds
• Container includes Composer for dependency management

Makefile

• make build - Build Docker image
• make install - Install dependencies
• make test - Run tests in Docker
• make test-coverage - Run with coverage report
• make shell - Debug shell access

CI/CD

• Added GitHub Actions workflow ci.yml
• Runs on push/PR to main, master, develop
• Two jobs: native PHP tests + Docker-based tests
• Codecov integration ready

Breaking Changes

• Requires PHP 8.4+
• composer.lock regenerated (run make install after pulling)

Known Issues

Third-party packages (corneltek/cliframework, guzzlehttp/guzzle, jippi/vault-php-sdk) trigger deprecation warnings on PHP 8.4 due to implicitly nullable parameters. These are warnings only and don't affect functionality.