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/revalidate/route.ts

@@ -0,0 +1,35 @@
+import { revalidatePath } from "next/cache"
+import { NextRequest } from "next/server"
+
+async function handler(request: NextRequest) {
+  const searchParams = request.nextUrl.searchParams
+  const secret = searchParams.get("secret")
+  const path = searchParams.get("path")
+
+  // Validate the revalidation secret.
+  if (secret !== process.env.DRUPAL_REVALIDATE_SECRET) {
+    return new Response("Invalid secret.", { status: 401 })
+  }
+
+  if (!path) {
+    return new Response("Missing path.", { status: 400 })
+  }
+
+  try {
+    revalidatePath(path)
+    return new Response(
+      JSON.stringify({ revalidated: true, now: Date.now() }),
+      {
+        status: 200,
+        headers: { "Content-Type": "application/json" },
+      }
+    )
+  } catch (error) {
+    return new Response(
+      JSON.stringify({ message: "Error revalidating.", error }),
+      { status: 500 }
+    )
+  }
+}
+
+export { handler as GET, handler as POST }