Fix file upload limit over 2MB in production with HTTPS

- Use printf instead of echo to correctly write php.ini with newlines
  (Alpine ash echo does not interpret \n, leaving the file malformed
  and PHP falling back to its 2MB default)
- Add nginx.conf with client_max_body_size 25M as front-end proxy
- Start nginx on port 8080 via supervisord; move artisan serve to
  internal port 8081 so nginx can proxy requests with proper limits

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

supervisord.conf

@@ -1,8 +1,13 @@
 [supervisord]
 nodaemon=true
 
+[program:nginx]
+command=nginx -g "daemon off;"
+autostart=true
+autorestart=true
+
 [program:laravel]
-command=php -c /app/php.ini /app/artisan serve --host=0.0.0.0 --port=8080
+command=php -c /app/php.ini /app/artisan serve --host=127.0.0.1 --port=8081
 autostart=true
 autorestart=true