add tunnel-only setup with Docker, including Dockerfile, docker-compose, and scripts

new-backend/docker-compose.tunnel-only.yml

@@ -0,0 +1,18 @@
+services:
+  tunnel:
+    build:
+      context: .
+      dockerfile: Dockerfile.tunnel-only
+    restart: unless-stopped
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
+    environment:
+      - TUNNEL_ORIGIN_CERT=/etc/cloudflared/cert.pem
+      - NO_AUTOUPDATE=true
+    # Isolated network
+    networks:
+      - monaco-tunnel-network
+
+networks:
+  monaco-tunnel-network:
+    driver: bridge