Closes AI-298

This PR adds the first step towards allowing to reorganize the threads
sidebar. Drag and drop should be supported in the near future, maybe
even replacing this entirely:

<img width="700" alt="Screenshot 2026-05-21 at 6  44@2x"
src="https://github.com/user-attachments/assets/db420466-2323-474b-ba41-17eb4da2cf84"
/>

Release Notes:

- Sidebar: Added the ability to reorder projects by moving them up and
down through the ellipsis menu.