feat(frontend): Add Docker containerization support for development and production

Implement complete Docker setup for Next.js 16 frontend with multi-stage builds,
hot reload support, and production optimizations.

Changes:
- Add Dockerfile with multi-stage build (deps, builder, development, production)
- Add .dockerignore to exclude unnecessary files from Docker context
- Add .env.local.example template for environment configuration
- Update next.config.ts with standalone output for production builds
- Add Docker convenience scripts to package.json for easy container management
- Support hot reload in development with volume mounts
- Use Node.js 20 Alpine for smaller image size
- Implement security best practices (non-root user in production)

Technical Details:
- Development stage: Full source mounted with hot reload via Turbopack
- Production stage: Standalone build with optimized static assets
- Image size: ~1.17GB (development), smaller for production
- Port: 3000 (maps to container port 3000)

Testing:
- Docker build verified for development target
- Container startup successful with Next.js 16.0.1
- HTTP 200 response confirmed on localhost:3000
- Hot reload functional with volume mounts

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

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

package.json

@@ -7,7 +7,19 @@
     "build": "next build",
     "start": "next start",
     "lint": "eslint",
-    "format": "prettier --write \"**/*.{ts,tsx,js,jsx,json,css,md}\""
+    "format": "prettier --write \"**/*.{ts,tsx,js,jsx,json,css,md}\"",
+    "docker:dev": "docker-compose up -d postgres redis backend",
+    "docker:all": "docker-compose up -d",
+    "docker:stop": "docker-compose down",
+    "docker:logs": "docker-compose logs -f frontend",
+    "docker:logs:backend": "docker-compose logs -f backend",
+    "docker:logs:all": "docker-compose logs -f",
+    "docker:restart": "docker-compose restart frontend",
+    "docker:restart:backend": "docker-compose restart backend",
+    "docker:clean": "docker-compose down -v && docker-compose up -d --build",
+    "docker:status": "docker-compose ps",
+    "docker:build": "docker build --target development -t colaflow-frontend:dev .",
+    "docker:build:prod": "docker build --target production -t colaflow-frontend:prod ."
   },
   "dependencies": {
     "@dnd-kit/core": "^6.3.1",