simplify: dedupe boilerplate and remove dead code across all layers

lib/view/pages/marianum_message/marianum_message_view.dart

@@ -2,7 +2,6 @@ import 'dart:typed_data';
 
 import 'package:flutter/material.dart';
 import 'package:syncfusion_flutter_pdfviewer/pdfviewer.dart';
-import 'package:url_launcher/url_launcher.dart';
 
 import '../../../api/marianumconnect/queries/get_newsletter_file/get_newsletter_file.dart';
 import '../../../widget/app_progress_indicator.dart';
@@ -39,20 +38,8 @@ class _MessageViewState extends State<MessageView> {
         return SfPdfViewer.memory(
           snapshot.data!,
           enableHyperlinkNavigation: true,
-          onHyperlinkClicked: (PdfHyperlinkClickedDetails e) {
-            showDialog(
-              context: context,
-              builder: (context) => ConfirmDialog(
-                title: 'Link öffnen',
-                content: 'Möchtest du den folgenden Link öffnen?\n${e.uri}',
-                confirmButton: 'Öffnen',
-                onConfirm: () => launchUrl(
-                  Uri.parse(e.uri),
-                  mode: LaunchMode.externalApplication,
-                ),
-              ),
-            );
-          },
+          onHyperlinkClicked: (PdfHyperlinkClickedDetails e) =>
+              ConfirmDialog.openBrowser(context, e.uri),
         );
       },
     ),