Add Drupal headless stack with Next.js frontend

- Add Next.js frontend service (nextjs) with Dockerfile and source
- Update docker-compose.yml: image names, Drupal 11.3.3, nextjs service
- Add docker-compose.override.yml.disabled for dev hot-reload
- Add install-headless-modules.sh for OAuth/JSON:API module setup
- Add README.md with full setup and configuration guide
- Update nginx/Dockerfile and nginx.conf.template for cms. subdomain
- Update drupal/Dockerfile PHP-FPM build args
- Gitignore **/.vscode/ to prevent IDE workspace files from being tracked

drupal/nginx/Dockerfile

@@ -3,6 +3,6 @@ FROM nginx:latest
 COPY ./nginx.conf.template /etc/nginx/nginx.conf.template
 
 ARG DOMAIN
-RUN sed 's|${DOMAIN}|'"$DOMAIN"'|g' /etc/nginx/nginx.conf.template > /etc/nginx/nginx.conf
+RUN envsubst '${DOMAIN}' < /etc/nginx/nginx.conf.template > /etc/nginx/nginx.conf
 
 ENTRYPOINT ["nginx", "-g", "daemon off;"]