implemented a guided notification permission flow triggered on the first Talk visit

lib/widget/confirm_dialog.dart

@@ -9,7 +9,10 @@ class ConfirmDialog extends StatelessWidget {
   final String content;
   final IconData? icon;
   final String confirmButton;
-  final String cancelButton;
+
+  /// Label of the cancel button. Set to `null` for a single-button dialog
+  /// (only the confirm action is rendered).
+  final String? cancelButton;
   final void Function()? onConfirm;
   final AsyncActionCallback? onConfirmAsync;
   final AsyncErrorBuilder? errorBuilder;
@@ -48,10 +51,11 @@ class ConfirmDialog extends StatelessWidget {
             ),
           ]
         : [
-            TextButton(
-              onPressed: () => Navigator.of(context).pop(),
-              child: Text(cancelButton),
-            ),
+            if (cancelButton != null)
+              TextButton(
+                onPressed: () => Navigator.of(context).pop(),
+                child: Text(cancelButton!),
+              ),
             TextButton(
               onPressed: () {
                 Haptics.confirm();