Rewrite with modern stack

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

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/package.json

@@ -0,0 +1,47 @@
+{
+  "name": "@gaplace/backend",
+  "version": "1.0.0",
+  "description": "GaPlace backend server with TypeScript, Redis, and WebSocket support",
+  "main": "dist/server.js",
+  "scripts": {
+    "dev": "tsx watch src/server.ts",
+    "build": "tsc",
+    "start": "node dist/server.js",
+    "clean": "rm -rf dist",
+    "type-check": "tsc --noEmit",
+    "lint": "eslint src --ext .ts",
+    "test": "jest",
+    "test:watch": "jest --watch"
+  },
+  "dependencies": {
+    "@gaplace/shared": "file:../shared",
+    "express": "^4.18.2",
+    "socket.io": "^4.7.4",
+    "redis": "^4.6.12",
+    "cors": "^2.8.5",
+    "helmet": "^7.1.0",
+    "compression": "^1.7.4",
+    "express-rate-limit": "^7.1.5",
+    "jsonwebtoken": "^9.0.2",
+    "bcryptjs": "^2.4.3",
+    "uuid": "^9.0.1",
+    "pg": "^8.11.3",
+    "dotenv": "^16.3.1",
+    "winston": "^3.11.0"
+  },
+  "devDependencies": {
+    "@types/express": "^4.17.21",
+    "@types/cors": "^2.8.17",
+    "@types/compression": "^1.7.5",
+    "@types/jsonwebtoken": "^9.0.5",
+    "@types/bcryptjs": "^2.4.6",
+    "@types/uuid": "^9.0.7",
+    "@types/pg": "^8.10.9",
+    "@types/node": "^20.10.6",
+    "@types/jest": "^29.5.11",
+    "jest": "^29.7.0",
+    "ts-jest": "^29.1.1",
+    "tsx": "^4.7.0",
+    "typescript": "^5.3.3"
+  }
+}