simplify: dedupe boilerplate and remove dead code across all layers

lib/view/pages/marianum_message/marianum_message_list_view.dart

@@ -6,6 +6,7 @@ import '../../../state/app/infrastructure/loadable_state/view/loadable_state_con
 import '../../../state/app/infrastructure/utility_widgets/bloc_module.dart';
 import '../../../state/app/modules/marianum_message/bloc/marianum_message_bloc.dart';
 import '../../../state/app/modules/marianum_message/bloc/marianum_message_state.dart';
+import '../../../widget/centered_leading.dart';
 import 'search_marianum_messages.dart';
 
 class MarianumMessageListView extends StatelessWidget {
@@ -40,12 +41,9 @@ class MarianumMessageListView extends StatelessWidget {
         child: (state, loading) => ListView.builder(
           itemCount: state.messageList.messages.length,
           itemBuilder: (context, index) {
-            var message = state.messageList.messages.toList()[index];
+            var message = state.messageList.messages[index];
             return ListTile(
-              leading: const Column(
-                mainAxisAlignment: MainAxisAlignment.center,
-                children: [Icon(Icons.newspaper)],
-              ),
+              leading: const CenteredLeading(Icon(Icons.newspaper)),
               title: Text(message.name, overflow: TextOverflow.ellipsis),
               subtitle: Column(
                 crossAxisAlignment: CrossAxisAlignment.start,

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),
         );
       },
     ),

lib/view/pages/marianum_message/search_marianum_messages.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart';
 
 import '../../../routing/app_routes.dart';
 import '../../../state/app/modules/marianum_message/bloc/marianum_message_state.dart';
+import '../../../widget/centered_leading.dart';
 import '../../../widget/placeholder_view.dart';
 
 class SearchMarianumMessages extends SearchDelegate<MarianumMessage?> {
@@ -45,10 +46,7 @@ class SearchMarianumMessages extends SearchDelegate<MarianumMessage?> {
       itemBuilder: (_, i) {
         final message = matches[i];
         return ListTile(
-          leading: const Column(
-            mainAxisAlignment: MainAxisAlignment.center,
-            children: [Icon(Icons.newspaper)],
-          ),
+          leading: const CenteredLeading(Icon(Icons.newspaper)),
           title: Text(message.name, overflow: TextOverflow.ellipsis),
           subtitle: Text('vom ${message.date}'),
           trailing: const Icon(Icons.arrow_right),