Clamp both _cachedContactsUnreadTotal and _cachedChannelsUnreadTotal
to >= 0 after decrementing in markContactRead() and markChannelRead().
This prevents the totals from going negative if the cache drifts
out-of-sync, which could cause UI badges to display incorrect values.

…ge styling

…hed contacts unread total

…om 10 to 11

When contacts are removed in removeContact, _handleContact, or _handleContactAdvert,
subtract their unread count from _cachedContactsUnreadTotal immediately so badge
counts reflect the true total without waiting for a full reload.

Resolved conflicts by accepting refactored state management from main:
- list_filter_widget.dart: Adopt sealed class pattern for filter actions
- contacts_screen.dart: Move state to UiViewStateService instead of local setState
- device_screen.dart: Accept deletion (consolidated into other screens in main)

Main branch includes significant improvements:
- TCP and USB transport support
- Service-based state management with UiViewStateService
- Translation support with message translation buttons
- Signal UI consistency improvements
- Additional language support (hu, ja, ko)
- Comprehensive test coverage
- Discovery screen refactoring

…r the lists; fixed unread indicator wasn't on all screens

merge dev into main

Unread badges for tabs