simplified code across the app and consolidated duplicated helpers

lib/widget/info_dialog.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 
+import '../api/errors/error_mapper.dart';
 import '../utils/clipboard_helper.dart';
 
 class InfoDialog {
@@ -40,4 +41,15 @@ class InfoDialog {
       },
     );
   }
+
+  /// Error dialog with the user-facing [message] (default: mapped from
+  /// [error]) plus the technical details when they add information.
+  static void showError(BuildContext context, Object error, {String? message}) {
+    final text = message ?? errorToUserMessage(error);
+    final details = errorToTechnicalDetails(error);
+    final body = details != null && details != text
+        ? '$text\n\n$details'
+        : text;
+    show(context, body, copyable: true, title: 'Fehler');
+  }
 }