Major refactor from simple HTML/JS app to modern full-stack TypeScript application:
## Architecture Changes
- Migrated to monorepo structure with workspaces (backend, frontend, shared)
- Backend: Node.js + Express + TypeScript + Socket.IO
- Frontend: Next.js 15.5 + React 19 + TypeScript + Tailwind CSS
- Shared: Common types and utilities across packages
## Key Features Implemented
- Real-time WebSocket collaboration via Socket.IO
- Virtual canvas with chunked loading for performance
- Modern UI with dark mode and responsive design
- Mock database system for easy development (Redis/PostgreSQL compatible)
- Comprehensive error handling and rate limiting
- User presence and cursor tracking
- Infinite canvas support with zoom/pan controls
## Performance Optimizations
- Canvas virtualization - only renders visible viewport
- Chunked pixel data loading (64x64 pixel chunks)
- Optimized WebSocket protocol
- Memory-efficient state management with Zustand
## Development Experience
- Full TypeScript support across all packages
- Hot reload for both frontend and backend
- Docker support for production deployment
- Comprehensive linting and formatting
- Automated development server startup
## Fixed Issues
- Corrected start script paths
- Updated environment configuration
- Fixed ESLint configuration issues
- Ensured all dependencies are properly installed
- Verified build process works correctly
