Add custom image handling and access policy management

- Implement tests for custom KVM and LXC image creation, ensuring invalid sources and architecture mismatches are rejected.
- Introduce access policy management in CLI, allowing configuration of allowed sources and trusted proxies.
- Add NAT network configuration with validation for RFC1918 compliance and subnet parsing.
- Create panel access policy management, including normalization and evaluation of access decisions based on client IPs and forwarded headers.
- Develop middleware for enforcing access policies in the server, returning appropriate responses for allowed and denied requests.
- Enhance custom image downloading and validation, ensuring integrity and security of downloaded root filesystem archives.
- Include comprehensive tests for all new functionalities to ensure reliability and correctness.

docs/guide/configuration.md

@@ -21,6 +21,23 @@ systemctl restart clicd
 journalctl -u clicd -n 100 --no-pager
 ```
 
+## 面板访问白名单 CLI
+
+```bash
+# 查看当前策略
+clicd access-policy show
+
+# 仅允许指定 IP/网段；反向代理地址按需填写
+clicd access-policy set \
+  --allow "203.0.113.10,192.168.1.0/24,2001:db8::/32" \
+  --trusted-proxy "127.0.0.1"
+
+# 关闭白名单限制
+clicd access-policy disable
+```
+
+也可以运行 `clicd cli`，在交互菜单中选择“面板访问白名单”。直接命令和交互菜单都会保存配置，并在服务运行时自动重启面板。
+
 ## 安全建议
 
 - 不要把 Web 面板直接暴露给不可信来源。

docs/guide/installation.md

@@ -17,6 +17,8 @@ CLICD 提供一键安装脚本。脚本默认安装 GitHub Releases 的最新版
 curl -fsSL https://raw.githubusercontent.com/MengMengCode/CLICD/main/install.sh | sudo sh
 ```
 
+安装器会分别询问 LXC 与 KVM 的 NAT 私网网段。直接回车时，脚本会扫描宿主机路由、网卡、网桥和 libvirt 网络，自动选择未冲突的 RFC1918 `/24` 网段；也可以输入 `172.28.40.0/24` 这类 CIDR。非交互安装可设置 `CLICD_LXC_SUBNET` 和 `CLICD_KVM_SUBNET`。
+
 脚本当前默认使用 `CLICD_VERSION=latest`，会按宿主架构下载 `releases/latest` 对应的 `clicd-linux-amd64.tar.gz` 或 `clicd-linux-arm64.tar.gz`。
 
 ## 安装指定版本