[FR]: Use collapsing header for topics screen

[tunjid]

Is there an existing issue for this?

• [X] I have searched the existing issues

Describe the problem

The header in the topics screen should be a collapsing toolbar and not a list item. This would also improve the accuracy of the scroll bars.

Describe the solution

Use a collapsing toolbar so the header item is not part of the list.

Additional context

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct