Allow default Windows install directory (e.g., C:\) to be set via environment variable

[dataliderapp]

Hi!
I’d like to suggest a feature: currently, the installation command generated for PowerShell on Windows uses a hardcoded default directory such as C:\ or C:\frp-panel.
It would be very helpful if this default directory could be set via an environment variable, similar to how other parameters in frp-panel can be configured.

This would make it easier to customize installation environments, especially in corporate or restricted settings where using the C:\ drive is not possible or recommended.

Suggestion:

Add an environment variable (for example, CLIENT_INSTALL_DIR) to define the default path used in generated install commands for Windows.

Thank you for your great work on this project!

[dataliderapp]

嗨！

我想建议一个功能：目前为 Windows PowerShell 生成的安装命令使用了硬编码的默认目录，例如 C:\ 或 C:\frp-panel。

如果能够像配置 frp-panel 其他参数一样，通过环境变量来设置此默认目录，将会非常有帮助。

这样可以更方便地定制安装环境，尤其是在企业或受限环境中无法或不推荐使用 C:\ 驱动器的场景下。

建议：

• 添加一个环境变量（例如 CLIENT_INSTALL_DIR），用于定义为 Windows 生成的安装命令中使用的默认路径。

感谢你们在该项目上的出色工作！