Replace UI storyboards

[steinbro]

The codebase has a mix of multiple generations of iOS UI implementation strategies , namely SwiftUI, UIKit, and storyboards. This is an unnecessarily complicated situation in its own right, but storyboards are the oldest and the most annoying to work with. They also pose a steep barrier to blind/low-vision contributors -- they may technically be supported by VoiceOver, but it's not easy to understand what's going on if you're not familiar with them. Ideally we could replace these views with SwiftUI. This would be a large undertaking, especially because they are the main (probably original) views.