Fix(backup): WebDAV Deletion Confirmation and List Refresh

[luosc]

Fix: WebDAV Deletion Confirmation and List Refresh

Description:

This PR addresses two key issues related to WebDAV backups:

1. Missing Confirmation on Deletion: Previously, deleting a remote WebDAV backup happened immediately without any user confirmation, leading to potential accidental data loss. A confirmation dialog has now been added to both Mobile (Android/iOS) and Desktop platforms.
2. Backup List Not Refreshing on Android: On Android devices, the list of remote backups did not refresh after a deletion, showing stale data. This has been resolved by automatically closing the menu upon confirmation, performing the deletion, and then re-opening the menu with the updated list.

Changes:

• Mobile (lib/features/backup/pages/backup_page.dart):
  • Added a confirmation dialog before deletion.
  • Implemented logic to close the current bottom sheet, show a loading indicator, perform the deletion, and then re-open the bottom sheet with the fresh list.
• Desktop (lib/desktop/setting/backup_pane.dart):
  • Added a confirmation dialog to the remote backup management dialog.
• Localization:
  • Added new translation keys backupPageDeleteConfirmTitle and backupPageDeleteConfirmContent to app_en.arb and app_zh.arb.

Testing:

• Verified on Android: The confirmation dialog appears, and after deletion, the menu reloads correctly reflecting the changes.
• Verified on macOS: The confirmation dialog appears correctly before deletion.

---

修复：WebDAV 删除确认及列表刷新问题

描述：

此 PR 修复了两个与 WebDAV 备份相关的问题：

1. 删除时缺少确认提示： 之前删除远程 WebDAV 备份时会立即执行，没有任何用户确认，容易导致误删。现在已在移动端 (Android/iOS) 和桌面端添加了删除确认对话框。
2. Android 端备份列表未刷新： 在 Android 设备上，删除操作后远程备份列表不会自动刷新，仍显示旧数据。通过在确认删除后自动关闭当前菜单，执行删除操作，然后重新打开菜单加载最新列表，解决了此问题。

变更：

• 移动端 (lib/features/backup/pages/backup_page.dart)：
  • 添加了删除前的确认对话框。
  • 实现了关闭当前底部菜单、显示加载提示、执行删除、然后重新打开底部菜单加载新列表的逻辑。
• 桌面端 (lib/desktop/setting/backup_pane.dart)：
  • 在远程备份管理对话框中添加了确认提示。
• 本地化：
  • 在 app_en.arb 和 app_zh.arb 中添加了新的翻译键值 backupPageDeleteConfirmTitle 和 backupPageDeleteConfirmContent。

测试：

• Android 验证：确认对话框正常显示，删除后菜单会自动重新加载并显示最新数据。
• macOS 验证：删除前能正确显示确认对话框。

[Chevey339]

这个编译的时候会报错
error: The method '_chooseImportOptionsDialog' isn't defined for the type '_BackupPageState'. (undefined_method at [Kelivo] lib\features\backup\pages\backup_page.dart:494)
error: The named parameter 'options' isn't defined. (undefined_named_parameter at [Kelivo] lib\features\backup\pages\backup_page.dart:496)

[luosc]

@Chevey339 感谢指出。我调查了，原因是：

• 这个改动是在颗粒化恢复feat基础上开发（RestoreOptions / _chooseImportOptionsDialog，见 PR Feat: 支持颗粒化备份恢复 (设置/供应商/聊天/文件) #240
• 我把该特性 rebase/cherry‑pick 到 origin/master 时没有带上依赖的 API 变更，master 里只有 _chooseImportModeDialog / mode，因此编译报错。Git 没有产生冲突，但 API 不匹配。

请问你希望的合并顺序是：
1）考虑先合并这个颗粒化恢复feat（PR #240），这样本改动无需修改即可生效；
还是
2）我先把本改动适配 origin/master（改回 _chooseImportModeDialog + mode），然后在 #240 再在本PR基础上改动？

[luosc]

@Chevey339

• 已经修复，现在已经不依赖PR Feat: 支持颗粒化备份恢复 (设置/供应商/聊天/文件) #240，可以先并了
• 在android和Mac上测试通过