Add Status filter for deleted tasks

### Describe your improvement idea or feature request

Currently the deleted tasks are shown in the filter when COMPLETED status is selected.
There can be a separate status filter for DELETED to provide more clarity.

### How would you like to see it implemented?

1. Add a deleted status filter.
2. Don't show deleted tasks in completed filter.

### Put here any screenshots or videos (optional)

_No response_

### How can we contact you (optional)

_No response_

### Would you like to work on this issue?

Yes

### By submitting this issue, I have confirmed that:

- [x] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.

首先在 Flutter 应用中定位任务状态筛选器，以及 COMPLETED 和已删除任务的映射。检查筛选器的呈现方式和任务的分类方式，然后验证 DELETED 是否可以单独选择，以及已删除的任务不再出现在 COMPLETED 下。

由索引模型根据 Issue 内容生成。