fix(189): disk-usage unmarshal failed when used capacity overflow

[KirCute]

Description / 描述

修改FreeSize的类型以兼容使用空间溢出的情况

Motivation and Context / 背景

Closes #1574

How Has This Been Tested? / 测试

Checklist / 检查清单

• I have read the CONTRIBUTING document.
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• I have requested review from relevant code authors using the "Request review" feature when applicable.
  我已在适当情况下使用"Request review"功能请求相关代码作者进行审查。
• I have updated the repository accordingly (If it’s needed).
  我已相应更新了相关仓库（若适用）。
  • OpenList-Frontend #XXXX
  • OpenList-Docs #XXXX