Fix build: externalize elysia packages, use standalone output, fix NODE_ENV

- Add serverExternalPackages for @elysiajs/static and elysia to prevent
  webpack from bundling dynamic imports that cause Html prerender error
- Use output: standalone for proper Docker deployment
- Comment out NODE_ENV=development in .env.example to avoid conflict
  with next build which requires NODE_ENV=production
- Set NODE_ENV=production before build step in Dockerfile
- Update runtime stage to use standalone output structure

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

.env.example

@@ -33,4 +33,4 @@ SESSION_PASSWORD="your_session_password_min_32_characters_long_secure"
 ELEVENLABS_API_KEY=your_elevenlabs_api_key
 
 # Environment (optional, defaults to development)
-NODE_ENV=development
+# NODE_ENV=development