fix: check if nginx is already installed before prompting for installation

configure_priv.sh

@@ -315,6 +315,9 @@ configure_nginx() {
         echo "deb-src [signed-by=/usr/share/keyrings/nginx.gpg] https://nginx.org/packages/ubuntu/ $(lsb_release -cs) nginx" | sudo tee -a /etc/apt/sources.list.d/nginx.list >/dev/null
     fi
     if confirm_action "要安装 nginx 吗？" "Y"; then
+        if command_exists nginx && ! confirm_action "检测到旧版 nginx 的存在 ($(nginx -v 2>&1))，是否继续安装？" "N"; then
+            return
+        fi
         sudo apt-get update
         sudo apt-get install nginx -y
         echo "nginx 版本: $(nginx -v 2>&1)"