fix(mount): prevent blank legacy mount page

[Suyunmeng]

Summary / 摘要

• Normalize legacy rclone.mount_config values to an empty object after settings load, preventing the mount view from indexing null and rendering blank.
  / 在加载设置后将旧版 rclone.mount_config 归一化为空对象，避免挂载视图索引 null 而出现白屏。

• Detect MacPorts and Apple Silicon Homebrew FUSE dylib locations, then pass CGOFUSE_LIBFUSE_PATH only to the rclone mount process when the user has not already set it.
  / 探测 MacPorts 和 Apple Silicon Homebrew 的 FUSE dylib 路径，并仅在用户未设置该变量时向 rclone 挂载进程传递 CGOFUSE_LIBFUSE_PATH。

• Raise the rclone download fallback to v1.72.1 so fallback builds support the FUSE library-path override.
  / 将 rclone 下载回退版本提升至 v1.72.1，确保回退构建支持 FUSE 库路径覆盖。

• This PR has breaking changes.
  / 此 PR 包含破坏性变更。

• This PR changes public API, config, storage format, or migration behavior.
  / 此 PR 修改了公开 API、配置、存储格式或迁移行为。

• This PR requires corresponding changes in related repositories.
  / 此 PR 需要关联仓库同步修改。

Related repository PRs / 关联仓库 PR:

• OpenList-Frontend:
• OpenList-Docs:

Related Issues / 关联 Issue

Fixes #115

Testing / 测试

• node --check scripts/prepare.js
  / node --check scripts/prepare.js
• git diff main...HEAD --check
  / git diff main...HEAD --check
• Rust formatting, checking, and clippy were not run because this environment has no installed Rust toolchain.
  / 由于当前环境未安装 Rust toolchain，未运行 Rust 格式检查、编译检查和 clippy。
• Manual test / 手动测试: Windows legacy-settings and macOS FUSE-path verification remain required.
  / 手动测试：仍需验证 Windows 旧设置与 macOS FUSE 路径。

Checklist / 检查清单

• I have read CONTRIBUTING.
  / 我已阅读 CONTRIBUTING。
• I confirm this contribution follows the repository license, contribution policy, and code of conduct.
  / 我确认此贡献符合仓库许可证、贡献规范和行为准则。
• I have formatted the changed code with gofmt, go fmt, or prettier where applicable.
  / 我已按适用情况使用 gofmt、go fmt 或 prettier 格式化变更代码。
• I have requested review from relevant maintainers or code owners where applicable.
  / 我已在适用情况下请求相关维护者或代码所有者审查。

AI Disclosure / AI 使用声明

• This PR includes AI-assisted content.
  / 此 PR 包含 AI 辅助内容。

Tools used / 使用工具:

• ChatGPT
• Codex
• GitHub Copilot
• Claude
• Gemini
• Other (please specify) / 其他（请注明）:

Usage scope / 使用范围:

• Code generation / 代码生成

• Refactoring / 重构

• Documentation / 文档

• Tests / 测试

• Translation / 翻译

• Review assistance / 审查辅助

• I have reviewed and validated all AI-assisted content included in this PR.
  / 我已审核并验证此 PR 中的所有 AI 辅助内容。

• I have ensured that all AI-assisted commits include Co-Authored-By attribution.
  / 我已确保所有 AI 辅助提交都包含 Co-Authored-By 归属信息。

• I can reproduce all AI-assisted content included in this PR without any AI tools.
  / 我可以在没有任何 AI 工具的情况下重现此 PR 中包含的所有 AI 辅助内容。