[Bug] install-cn.ps1 使用清华源安装依赖出现 403，手动进venv改用阿里云源下载后成功

## 问题描述
运行 install-cn.ps1 安装依赖时，清华源报 403 错误。
## 复现步骤
1.从 GitHub 克隆 Akegarasu/lora-scripts 仓库。
2.右键install-cn.ps1 -> 使用PowerShell运行
## 环境信息
- 操作系统:Windows11
- Python version: 3.11.8 和3.13.13(均报错)
## 错误日志
```
ERROR: HTTP error 403 while getting https://pypi.tuna.tsinghua.edu.cn/packages/eb/62/c321f13b5ba1819fc8dca456c7fce578da2dcfecff1abbf0eaddf8406c0f/pandas-3.0.3-cp311-cp311-win_amd64.whl (from https://pypi.tuna.tsinghua.edu.cn/simple/pandas/) (requires-python:>=3.11)
ERROR: Could not install requirement pandas from https://pypi.tuna.tsinghua.edu.cn/packages/eb/62/c321f13b5ba1819fc8dca456c7fce578da2dcfecff1abbf0eaddf8406c0f/pandas-3.0.3-cp311-cp311-win_amd64.whl (from -r requirements.txt (line 30)) because of HTTP error 403 Client Error: Forbidden for url: https://pypi.tuna.tsinghua.edu.cn/packages/eb/62/c321f13b5ba1819fc8dca456c7fce578da2dcfecff1abbf0eaddf8406c0f/pandas-3.0.3-cp311-cp311-win_amd64.whl for URL https://pypi.tuna.tsinghua.edu.cn/packages/eb/62/c321f13b5ba1819fc8dca456c7fce578da2dcfecff1abbf0eaddf8406c0f/pandas-3.0.3-cp311-cp311-win_amd64.whl (from https://pypi.tuna.tsinghua.edu.cn/simple/pandas/) (requires-python:>=3.11)
```
## 临时解决方案:手动安装
1.打开PowerShell
2.cd your_path/lora_scripts 进入 lora_scripts 文件夹
3. .\venv\Scripts\activate 激活脚本报错前创造的虚拟环境
4.pip install -r requirements.txt -i http://mirrors.aliyun.com/pypi/simple --trusted-host mirrors.aliyun.com

## 建议
为脚本增加备用镜像源和403报错自动切换备用源机制