- Remove .toolbarBackground(.visible) from all NavigationStack views:
this modifier suppresses large title rendering in iOS 26.
- Discover: switch to always-present List + overlay pattern so SwiftUI
never loses the scroll context during loading transitions.
- Discover, Notifications, Groups: use .inline title mode; the tab bar
already identifies these screens, large titles are redundant.
- RootView: add .toolbarColorScheme propagation for nav bar foreground.
- Settings sheet: apply theme background and toolbar color to the Form.