feat: add on-demand folder size calculation in file manager (#1201)

* Initial plan

* feat: add folder size calculation feature with "Calculate" link

- Backend: Add Size API to calculate directory size
- Backend: Modify formatDir to return empty size for directories
- Frontend: Show "Calculate" link for directories instead of size
- Frontend: Add loading spinner during calculation
- Frontend: Cache calculated sizes until path changes
- Add translations for Calculate and Failed to calculate size

Co-authored-by: devhaozi <115467771+devhaozi@users.noreply.github.com>

* fix: lint

* fix: 优化

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: devhaozi <115467771+devhaozi@users.noreply.github.com>
Co-authored-by: 耗子 <haozi@loli.email>

web/src/api/panel/file/index.ts

@@ -22,6 +22,8 @@ export default {
     http.Post('/file/remote_download', { path, url }),
   // 获取文件信息
   info: (path: string): any => http.Get('/file/info', { params: { path } }),
+  // 获取目录/文件大小
+  size: (path: string): any => http.Get('/file/size', { params: { path } }),
   // 修改文件权限
   permission: (path: string, mode: string, owner: string, group: string): any =>
     http.Post('/file/permission', { path, mode, owner, group }),