This PR adds the ability to favorite a channel in the collab panel. Note
that favorited channels:
- appear at the very top of the panel
- also appear in their normal place in the tree
- are not stored in settings but rather in the local key-value store

<img width="500" height="618" alt="Screenshot 2026-03-25 at 1  11@2x"
src="https://github.com/user-attachments/assets/dda8d5ae-7b45-4846-acc9-4a940b487ac4"
/>

Release Notes:

- Collab: Added the ability to favorite channels in the collab panel.