add tunnel-only setup with host network mode, including updated Dockerfile, docker-compose, and configuration files

new-backend/docker-compose.tunnel-only-v2.yml

@@ -0,0 +1,11 @@
+services:
+  tunnel:
+    build:
+      context: .
+      dockerfile: Dockerfile.tunnel-only
+    restart: unless-stopped
+    # Use host network mode to directly access localhost:9090
+    network_mode: "host"
+    environment:
+      - TUNNEL_ORIGIN_CERT=/etc/cloudflared/cert.pem
+      - NO_AUTOUPDATE=true