Feature/config security and core refactor

[walid-khalafi]

This merge integrates multiple improvements to the project's core:

• Enhanced .htaccess with professional English comments and added security headers (X-Content-Type-Options, X-Frame-Options, Referrer-Policy, X-XSS-Protection) while preserving existing rewrite rules.
• Revamped README.md with detailed project description, installation instructions, and security best practices.
• Refactored index.php with clear, professional English documentation comments, improved logging format, safer response handling, and cleaner cURL request preparation.

No breaking changes introduced. Application behavior remains functionally identical, with improved maintainability and security.