Revert standalone output, keep serverExternalPackages fix

- Remove output: standalone to keep migration/seed workflow
- Restore original Dockerfile structure with full node_modules copy
- Keep serverExternalPackages for @elysiajs/static and elysia to fix
  the Html prerender error caused by dynamic import in @elysiajs/static
- Keep NODE_ENV=production before build step

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

next.config.ts

@@ -1,7 +1,6 @@
 import type { NextConfig } from "next";
 
 const nextConfig: NextConfig = {
-  output: 'standalone',
   serverExternalPackages: ['@elysiajs/static', 'elysia'],
   experimental: {},
   allowedDevOrigins: [