MultiTimer: 多个计时器 · 更新记录

Fixed some bugs in working with iCloud and widgets.

- Fixed an iCloud error
- Fixed interface bugs

- Fixed a Live Activity bug

- Added countup timer support for LiveActivity.
- LiveActivity's appearance has been updated + buttons have been added.
- Detailed countup timer history entries now account for time additions and subtractions.
- Added a setting to automatically clear the timer history.
- Improved XML export/import.

- Fixed some bugs