feat(ui): new user ux improvements

[psychedelicious]

Summary

• Update viewer styling to have a menubar-ish header. Also used for image comparison.
• Set default control weight & end step % to 0.75.
• Add " (recommended)" to the "Balanced" control mode label.
• Add tooltip to layer preview image showing the layer at the same size as the boards/style presets image preview tooltips.
• Add empty state for control layers guiding user to upload an image, drag an image from gallery or start drawing.
• Add "simple" mode for control layers filtering, triggered when you select a control model. This automatically selects and processes the default filter for that model, if a default exists. If the user clicks Advanced, they get the full filter settings UI.
• Default control layers to no model selection.

Related Issues / Discussions

Offline discussion.

QA Instructions

Try the changes out.

Merge Plan

n/a

Checklist

• The PR has a short but descriptive title, suitable for a changelog