Add comprehensive CLAUDE.md documentation for AI assistants

This document provides detailed information about the codebase structure,
architecture, development workflows, and conventions for AI assistants
working with this repository.

Key sections include:
- Project overview and technology stack
- Repository structure and component organization
- Architecture and design patterns
- Code conventions and style guidelines
- Testing patterns and guidelines
- Build and development workflows
- TLD configuration details
- Common development tasks and pitfalls
- Troubleshooting guide and contribution guidelines

Author: claude