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/docker-compose.override.yml.disabled

@@ -0,0 +1,27 @@
+# Development overrides: bind mounts for Next.js hot reload.
+# Loaded automatically by Docker Compose. Remove or rename to disable.
+services:
+  nextjs:
+    build:
+      context: ./nextjs
+      dockerfile: Dockerfile
+      target: development
+      args:
+        NEXT_PUBLIC_DRUPAL_BASE_URL: https://cms.${DOMAIN}
+    volumes:
+      - ./nextjs:/app
+      - nextjs-node-modules:/app/node_modules
+      - nextjs-next-cache:/app/.next
+    ports:
+      - "9229:9229"
+    environment:
+      - NODE_ENV=production
+      - HOSTNAME=0.0.0.0
+      - WATCHPACK_POLLING=false
+      - NODE_OPTIONS=--inspect=0.0.0.0:9229
+
+volumes:
+  nextjs-node-modules:
+    name: drupal-nextjs-node-modules
+  nextjs-next-cache:
+    name: drupal-nextjs-next-cache