loading state and error handling refactor

lib/widget/confirm_dialog.dart

@@ -1,14 +1,30 @@
 import 'package:flutter/material.dart';
 import 'package:url_launcher/url_launcher.dart';
 
+import 'async_action_button.dart';
+
 class ConfirmDialog extends StatelessWidget {
   final String title;
   final String content;
   final IconData? icon;
   final String confirmButton;
   final String cancelButton;
-  final void Function() onConfirm;
-  const ConfirmDialog({super.key, required this.title, this.content = '', this.icon, this.confirmButton = 'Ok', this.cancelButton = 'Abbrechen', required this.onConfirm});
+  final void Function()? onConfirm;
+  final AsyncActionCallback? onConfirmAsync;
+  final AsyncErrorBuilder? errorBuilder;
+
+  const ConfirmDialog({
+    super.key,
+    required this.title,
+    this.content = '',
+    this.icon,
+    this.confirmButton = 'Ok',
+    this.cancelButton = 'Abbrechen',
+    this.onConfirm,
+    this.onConfirmAsync,
+    this.errorBuilder,
+  }) : assert(onConfirm != null || onConfirmAsync != null,
+          'ConfirmDialog requires either onConfirm or onConfirmAsync');
 
   void asDialog(BuildContext context) {
     showDialog(context: context, builder: build);
@@ -16,20 +32,33 @@ class ConfirmDialog extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) => AlertDialog(
-      icon: icon != null ? Icon(icon) : null,
-      title: Text(title),
-      content: Text(content),
-      actions: [
-        TextButton(onPressed: () {
-          Navigator.of(context).pop();
-        }, child: Text(cancelButton)),
-        TextButton(onPressed: () {
-          Navigator.of(context).pop();
-          onConfirm();
-        }, child: Text(confirmButton)),
-      ],
-    );
-  
+        icon: icon != null ? Icon(icon) : null,
+        title: Text(title),
+        content: Text(content),
+        actions: onConfirmAsync != null
+            ? [
+                AsyncDialogAction(
+                  confirmLabel: confirmButton,
+                  cancelLabel: cancelButton,
+                  onConfirm: onConfirmAsync!,
+                  errorBuilder: errorBuilder,
+                ),
+              ]
+            : [
+                TextButton(
+                  onPressed: () => Navigator.of(context).pop(),
+                  child: Text(cancelButton),
+                ),
+                TextButton(
+                  onPressed: () {
+                    Navigator.of(context).pop();
+                    onConfirm!();
+                  },
+                  child: Text(confirmButton),
+                ),
+              ],
+      );
+
   static void openBrowser(BuildContext context, String url) {
     showDialog(
       context: context,