docs: add comprehensive README for Claude Code Web Interface
Add complete README.md with:
- Feature overview and highlights
- Quick start guide (3-minute setup)
- Installation instructions (systemd, PM2)
- Configuration guide
- Complete usage guide (sessions, projects, terminal, XML tags)
- Full API reference with examples
- Development guide with project structure
- Database schema documentation
- Troubleshooting section
- Contributing guidelines
- License and acknowledgments
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
