feat: Add functionality to delete all discovered contacts

- Implemented a new method to remove all discovered contacts from the list.
- Added confirmation dialog for deleting all discovered contacts in the discovery screen.
- Updated localization files to include new strings for deleting all discovered contacts.
- Refactored contact import logic to streamline the process.
- Enhanced the discovery handling to notify users appropriately based on settings.

lib/l10n/app_localizations_nl.dart

@@ -38,6 +38,9 @@ class AppLocalizationsNl extends AppLocalizations {
   @override
   String get common_delete => 'Verwijderen';
 
+  @override
+  String get common_deleteAll => 'Alles verwijderen';
+
   @override
   String get common_close => 'Sluiten';
 
@@ -3180,4 +3183,12 @@ class AppLocalizationsNl extends AppLocalizations {
 
   @override
   String get discoveredContacts_deleteContact => 'Contact verwijderen';
+
+  @override
+  String get discoveredContacts_deleteContactAll =>
+      'Verwijder alle ontdekte contacten';
+
+  @override
+  String get discoveredContacts_deleteContactAllContent =>
+      'Weet u zeker dat u alle ontdekte contacten wilt verwijderen?';
 }