Add UX polish: loading states, empty states, toast notifications, and comprehensive documentation
- Create reusable Loading and EmptyState components with brutalist design
- Replace basic spinners with styled Loading component throughout app
- Add EmptyState for no files/repos scenarios with helpful messaging
- Install and integrate sonner for toast notifications
- Add toast notifications for save errors, publish success/failures
- Update DashboardApp to include Toaster with custom styling
- Improve error handling in EditorContainer and SetupWizard
- Create comprehensive README.md with features, setup, architecture
- Create detailed SETUP.md with deployment guides and troubleshooting
- Update .env.example to match backend environment variables
- Fix docker-compose.yml environment variables and health checks
- Update frontend port from 4321 to 3000 in docker-compose
This completes Phase 4 polish and documentation tasks.