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

app/server/api/health.get.ts

@@ -0,0 +1,12 @@
+/**
+ * Health check endpoint for container monitoring
+ * 
+ * Returns 200 OK if the server is running
+ */
+export default defineEventHandler(() => {
+  return {
+    status: 'ok',
+    timestamp: new Date().toISOString(),
+    uptime: process.uptime()
+  }
+})