Backend Integration, Optimization, and Documentation

[h0z3yn]

This pull request introduces several key improvements to the existing Telegram Mini App example. It now includes back-end functionality, optimizations, and extensive documentation. These changes enhance both the functionality and clarity of the project for future contributors.

Changes:

Back-end Integration: Added server-side validation of initData using PHP, including HMAC verification and database interaction for user authentication. Code Optimization: Improved code structure and readability across both front-end (JavaScript) and back-end (PHP). Detailed Documentation: Updated the README file to include detailed instructions for setup, including database configuration, project structure overview, and usage guide. Modular Structure: Enhanced the overall organization by breaking down functions and separating concerns (e.g., validation, modal alerts, link management, and dynamic UI adjustments).

Looking forward to your feedback!

Thank you for the opportunity to contribute!

Let me know if you'd like any changes to this!