Fetch server-side settings on app launch via new serverSettingsProvider.
Hide News from bottom sheet and NavigationRail when RSS is disabled.
Skip news card rendering in briefing messages when disabled.
Refactor tab navigation to use dynamic tabs list and route-based refresh.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
On shell mount, reads the IANA timezone from the device via
flutter_timezone and POSTs it to PUT /api/settings as user_timezone.
Mirrors the web app's App.vue behaviour so briefing events and the
chat route use the correct local time on Android.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>