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/nextjs/app/api/draft/route.ts

@@ -0,0 +1,7 @@
+import { drupal } from "@/lib/drupal"
+import { enableDraftMode } from "next-drupal/draft"
+import type { NextRequest } from "next/server"
+
+export async function GET(request: NextRequest): Promise<Response | never> {
+  return enableDraftMode(request, drupal)
+}