feat: UX polish, localization, advert relocation, and map filter fixes

- i18n: translate connection screen + chat tab keys into 13 locales;
  add "Send my contact" (advert) strings in all locales
- feat: move self-advert from home header into composer "+" action menu
  (new lib/utils/advert_helper.dart, always shows Flood/Direct sheet)
- fix: hide-repeaters map toggle was bypassed in simple mode
- fix: simple mode map now shows only favourite chat contacts
- fix: wrap ListTiles in Material (contact_tile secondary actions,
  inferred contact group card) to satisfy Flutter ink assertions
- device-authoritative contact/channel sync and UX review fixes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/main.dart

@@ -34,6 +34,7 @@ import 'screens/discovery_screen.dart';
 import 'screens/home_screen.dart';
 import 'screens/welcome_wizard_screen.dart';
 import 'theme/app_theme.dart';
+import 'utils/toast_logger.dart';
 import 'l10n/app_localizations.dart';
 
 Future<void> main() async {
@@ -395,6 +396,7 @@ class _MeshCoreSarAppState extends State<MeshCoreSarApp> {
         final systemBrightness = MediaQuery.platformBrightnessOf(context);
         final materialApp = MaterialApp(
           navigatorKey: _navigatorKey,
+          scaffoldMessengerKey: rootScaffoldMessengerKey,
           key: ValueKey<String?>(
             '${_locale?.languageCode ?? 'system'}_${_themeMode.name}',
           ),