feat(docker): implement full frontend Next.js containerization and multi-service docker-compose

- Create multi-stage standalone Dockerfile for Next.js frontend (node:20-alpine, non-root nextjs:nodejs user)
- Configure output: 'standalone' in refer_landing_page/next.config.js
- Add refer_landing_page/.dockerignore for build context optimization
- Wire anl-backend and anl-frontend services in root docker-compose.yml with healthchecks, network dependencies, and persistent volume storage

refer_landing_page/.dockerignore

@@ -0,0 +1,14 @@
+Dockerfile
+.dockerignore
+node_modules
+npm-debug.log
+README.md
+.next
+.git
+.gitignore
+.env*.local
+tests
+scripts
+.mam
+.agents
+.venv