fix: suppress output when backing up existing server binary during deployment

Co-authored-by: Copilot <copilot@github.com>

.drone.yml

@@ -20,7 +20,7 @@ steps:
       # 创建部署目录
       - mkdir -p /opt/short-link/frontend
       # 拷贝编译产物
-      - mv /opt/short-link/short-link-server /opt/short-link/short-link-server.bak
+      - mv /opt/short-link/short-link-server /opt/short-link/short-link-server.bak >/dev/null 2>&1 || true
       - cp backend/short-link-server /opt/short-link/short-link-server
       - cp -r frontend/dist/* /opt/short-link/frontend/
       - cp Caddyfile /root/projects/_conf/short-link.conf