UI tweak: disable prioritization

This is probably not super important... but Michael N. mentioned today that for the simplest use cases, people already know approximately where they want to design, and won't be interested in the prioritization tool at all.

Instead of having a "Prioritization: None" dropdown option, we could have the entire "prioritization section" be a collapsable section.

If we find that this is in fact *most* user, we could have it unchecked by default and save a little vertical space.

Again, this doesn't seem very urgent compared to some of the other changes we want to make, but wanted to get it down.

Look for the prioritization UI component in the frontend code, likely in a Rust file handling the UI layout or settings panel. Identify how the prioritization section is currently rendered (likely as a dropdown) and modify it to be a collapsible section with a default unchecked state. Test the change in the web interface to ensure the section collapses/expands correctly and the UI saves space as intended.

Written by the indexing model from the issue text.