Add proper technical documentation

jeremah
2025-01-22T07:34:35Z

*Created by: Krugou*

Add technical documentation to `backend/README.md` and `frontend/README.md`.

* **Backend Documentation**
- Add a section for API documentation, detailing available endpoints, request parameters, and response formats.
- Add a section for error handling, explaining the comprehensive error handling mechanisms and custom error types.
- Add a section for security best practices, outlining input validation, sanitization, authentication, authorization, rate limiting, and logging.

* **Frontend Documentation**
- Add a section for component documentation, describing the purpose, props, and usage of each component.
- Add a section for state management, explaining the state management solution and its structure.
- Add a section for testing, detailing the testing strategy, tools used, and types of tests included (unit, integration, end-to-end).