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

docker-compose.yml

@@ -14,13 +14,37 @@ services:
       - GIN_MODE=release
       - CORS_ALLOW_ORIGINS=*
       - AUTO_MIGRATE=true
+      - ADMIN_TOKEN=${ADMIN_TOKEN:-anl-admin-secret-token-2026}
     volumes:
       - anl-db-data:/app/data
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8080/api/v1/health"]
-      interval: 30s
+      interval: 10s
       timeout: 3s
       retries: 3
+      start_period: 5s
+
+  anl-frontend:
+    build:
+      context: ./refer_landing_page
+      dockerfile: Dockerfile
+    container_name: anl-frontend-web
+    restart: unless-stopped
+    ports:
+      - "3000:3000"
+    environment:
+      - NODE_ENV=production
+      - PORT=3000
+      - NEXT_PUBLIC_API_URL=http://localhost:8080/api/v1
+    depends_on:
+      anl-backend:
+        condition: service_healthy
+    healthcheck:
+      test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider", "http://localhost:3000"]
+      interval: 15s
+      timeout: 3s
+      retries: 3
+      start_period: 10s
 
 volumes:
   anl-db-data: