fix(user-management): adjust role selection logic in user filter dialog

- Remove toggling logic for dashboard role selection
- Allow direct setting of role, including null value

Author: fulleni

lib/user_management/widgets/user_filter_dialog/bloc/user_filter_dialog_bloc.dart

@@ -71,13 +71,9 @@ class UserFilterDialogBloc
     UserFilterDialogDashboardRoleChanged event,
     Emitter<UserFilterDialogState> emit,
   ) {
-    // This logic allows toggling the selection. If the user clicks the
-    // currently selected role, it deselects it (sets to null), which
-    // corresponds to the 'Any' state.
-    final newRole = state.dashboardRole == event.dashboardRole
-        ? null
-        : event.dashboardRole;
-    emit(state.copyWith(dashboardRole: newRole));
+    // Directly set the state to the selected role. The UI's `onSelected`
+    // will pass `null` when 'Any' is tapped.
+    emit(state.copyWith(dashboardRole: event.dashboardRole));
   }
 
   /// Resets all temporary filter selections in the dialog.

lib/user_management/widgets/user_filter_dialog/user_filter_dialog.dart

@@ -154,7 +154,6 @@ class _UserFilterDialogState extends State<UserFilterDialog> {
                     values: const [
                       DashboardUserRole.admin,
                       DashboardUserRole.publisher,
-                      DashboardUserRole.none,
                     ],
                     onSelected: (value) =>
                         context.read<UserFilterDialogBloc>().add(