refactored broad range of the application, split files, modularized calendar and file views, centralized bottom sheets and clipboard handling, and implemented unit test coverage

lib/view/pages/marianum_message/marianum_message_view.dart

@@ -4,6 +4,7 @@ import 'package:url_launcher/url_launcher.dart';
 
 import '../../../state/app/modules/marianum_message/bloc/marianum_message_state.dart';
 import '../../../widget/confirm_dialog.dart';
+import '../../../widget/info_dialog.dart';
 
 class MessageView extends StatefulWidget {
   final String basePath;
@@ -26,15 +27,11 @@ class _MessageViewState extends State<MessageView> {
         enableHyperlinkNavigation: true,
         onDocumentLoadFailed: (PdfDocumentLoadFailedDetails e) {
           Navigator.of(context).pop();
-          showDialog(context: context, builder: (context) => AlertDialog(
-              title: const Text('Fehler beim öffnen'),
-              content: Text("Dokument '${widget.message.name}' konnte nicht geladen werden:\n${e.description}"),
-              actions: [
-                TextButton(onPressed: () {
-                  Navigator.of(context).pop();
-                }, child: const Text('Ok'))
-              ],
-            ));
+          InfoDialog.show(
+            context,
+            "Dokument '${widget.message.name}' konnte nicht geladen werden:\n${e.description}",
+            title: 'Fehler beim öffnen',
+          );
         },
         onHyperlinkClicked: (PdfHyperlinkClickedDetails e) {
           showDialog(