fix: update Linux bootable to Ubuntu 24.04.4, add format-persistence.sh, rewrite guide

- Update all 24.04.2 references to 24.04.4 (ISO name, URLs, SHA256, docs)
- Add format-persistence.sh to bootable/linux-setup/ (from working E: drive)
- Rewrite website guide.html Linux tutorial: Linux Mint + Rufus → Ventoy + Ubuntu

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bootable/TROUBLESHOOTING.md

@@ -18,7 +18,7 @@
 1. 脚本会自动尝试多个国内镜像（清华、阿里、中科大）
 2. 如果全部失败，可以手动下载：
    - 访问 https://mirrors.tuna.tsinghua.edu.cn/ubuntu-releases/24.04/
-   - 下载 `ubuntu-24.04.2-desktop-amd64.iso`
+   - 下载 `ubuntu-24.04.4-desktop-amd64.iso`
    - 放到 `bootable/.download-cache/` 目录
 3. 重新运行 `2-download-iso.ps1`