Hide waiting tasks

### Describe your improvement idea or feature request

You can add a wait date to a task, which has the effect of hiding the task from you until that date.

So the app should also do the same by default.

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

All waiting tasks are hidden by default
Pending and waiting are two separate entitites (just as they appear when you would run the example command task X where X is the ID of the task)
Also see: https://github.com/CCExtractor/taskwarrior-flutter/issues/337

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

None

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

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

Start by reviewing the task filtering and list-display entry points, then read the related issue #337 for context on waiting tasks. Confirm how pending and waiting tasks are represented, hide waiting tasks by default while keeping pending tasks visible, and verify the behavior in the app's task list.

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