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

test/extensions/date_time_test.dart

@@ -0,0 +1,61 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:jiffy/jiffy.dart';
+import 'package:marianum_mobile/extensions/date_time.dart';
+
+void main() {
+  setUpAll(() async {
+    // Jiffy needs locale data once before any formatting calls.
+    await Jiffy.setLocale('de');
+  });
+
+  group('IsSameDay', () {
+    test('isSameDay matches by year/month/day, ignoring time', () {
+      final a = DateTime(2026, 5, 8, 9, 30);
+      final b = DateTime(2026, 5, 8, 22, 0);
+      expect(a.isSameDay(b), isTrue);
+    });
+
+    test('isSameDay differs across midnight', () {
+      final a = DateTime(2026, 5, 8, 23, 59);
+      final b = DateTime(2026, 5, 9, 0, 0);
+      expect(a.isSameDay(b), isFalse);
+    });
+
+    test('isSameOrAfter is inclusive', () {
+      final a = DateTime(2026, 5, 8, 12);
+      final b = DateTime(2026, 5, 8, 12);
+      expect(a.isSameOrAfter(b), isTrue);
+      expect(a.add(const Duration(seconds: 1)).isSameOrAfter(b), isTrue);
+      expect(a.subtract(const Duration(seconds: 1)).isSameOrAfter(b), isFalse);
+    });
+  });
+
+  group('DateTimeFormatting', () {
+    final dt = DateTime(2026, 5, 8, 9, 7);
+
+    test('formatHm pads hours and minutes to two digits', () {
+      expect(dt.formatHm(), '09:07');
+    });
+
+    test('formatDate uses dd.MM.yyyy', () {
+      expect(dt.formatDate(), '08.05.2026');
+    });
+
+    test('formatDateTime combines date and time', () {
+      expect(dt.formatDateTime(), '08.05.2026 09:07');
+    });
+
+    test('formatDateShort drops the year', () {
+      expect(dt.formatDateShort(), '08.05.');
+    });
+
+    test('formatDateShortHm combines short date and time', () {
+      expect(dt.formatDateShortHm(), '08.05. 09:07');
+    });
+
+    test('timeRangeTo joins start and end with a hyphen', () {
+      final end = dt.add(const Duration(minutes: 45));
+      expect(dt.timeRangeTo(end), '09:07 - 09:52');
+    });
+  });
+}