feat: create production Dockerfile (#37)

- Multi-stage build for optimal image size
- Alpine Linux base (~220MB total)
- Non-root user for security (nodejs:1001)
- dumb-init for proper signal handling
- Built-in health check endpoint
- Production dependencies only
- Comprehensive .dockerignore
- Health check API endpoint
- Docker deployment documentation

Features:
- Optimized layer caching
- Secure non-root execution
- Container health monitoring
- ~220MB final image size
- Ready for Kubernetes/Docker Compose

Closes #37

docker/README.md

@@ -0,0 +1,90 @@
+# Docker Deployment
+
+## Production Dockerfile
+
+The production Dockerfile uses a multi-stage build for optimized image size and security.
+
+### Build the image
+
+```bash
+docker build -t pantry:latest -f Dockerfile .
+```
+
+### Run the container
+
+```bash
+docker run -d \
+  --name pantry \
+  -p 3000:3000 \
+  -e NUXT_PUBLIC_SUPABASE_URL=https://your-project.supabase.co \
+  -e NUXT_PUBLIC_SUPABASE_ANON_KEY=your-anon-key \
+  pantry:latest
+```
+
+### Environment Variables
+
+Required:
+- `NUXT_PUBLIC_SUPABASE_URL` - Your Supabase project URL
+- `NUXT_PUBLIC_SUPABASE_ANON_KEY` - Your Supabase anon/public key
+
+Optional:
+- `PORT` - Port to listen on (default: 3000)
+- `HOST` - Host to bind to (default: 0.0.0.0)
+
+### Health Check
+
+The container includes a health check endpoint at `/api/health`
+
+```bash
+curl http://localhost:3000/api/health
+```
+
+Expected response:
+```json
+{
+  "status": "ok",
+  "timestamp": "2026-02-25T00:00:00.000Z",
+  "uptime": 123.456
+}
+```
+
+### Image Features
+
+- **Multi-stage build**: Separate build and runtime stages
+- **Alpine Linux**: Minimal base image (~50MB base)
+- **Non-root user**: Runs as unprivileged user (nodejs:1001)
+- **dumb-init**: Proper signal handling and zombie reaping
+- **Health checks**: Built-in container health monitoring
+- **Production-optimized**: Only production dependencies included
+
+### Image Size
+
+Approximate sizes:
+- Base Alpine + Node.js: ~50MB
+- Dependencies: ~150MB
+- Built app: ~20MB
+- **Total**: ~220MB
+
+### Security
+
+- Runs as non-root user (nodejs)
+- No unnecessary packages
+- Minimal attack surface
+- Regular security updates via Alpine base
+
+### Troubleshooting
+
+View logs:
+```bash
+docker logs pantry
+```
+
+Interactive shell:
+```bash
+docker exec -it pantry sh
+```
+
+Check health:
+```bash
+docker inspect --format='{{json .State.Health}}' pantry
+```