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/widget/async_action_controller_test.dart

@@ -0,0 +1,82 @@
+import 'dart:async';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/widget/async_action_button.dart';
+
+void main() {
+  group('AsyncActionController.run', () {
+    test('toggles busy true while running and false after success', () async {
+      final controller = AsyncActionController();
+      addTearDown(controller.dispose);
+
+      var seenBusyInsideCallback = false;
+      final ok = await controller.run(() async {
+        seenBusyInsideCallback = controller.busy;
+      });
+
+      expect(seenBusyInsideCallback, isTrue,
+          reason: 'busy must be true while the callback is running');
+      expect(ok, isTrue);
+      expect(controller.busy, isFalse);
+      expect(controller.error, isNull);
+    });
+
+    test('captures mapped error message on failure and returns false', () async {
+      final controller = AsyncActionController();
+      addTearDown(controller.dispose);
+
+      final ok = await controller.run(
+        () async => throw Exception('boom'),
+        errorBuilder: (e) => 'custom: $e',
+      );
+
+      expect(ok, isFalse);
+      expect(controller.busy, isFalse);
+      expect(controller.error, contains('custom:'));
+      expect(controller.error, contains('boom'));
+    });
+
+    test('rejects re-entry while busy', () async {
+      final controller = AsyncActionController();
+      addTearDown(controller.dispose);
+
+      final firstStarted = Completer<void>();
+      final firstCanFinish = Completer<void>();
+      final firstFuture = controller.run(() async {
+        firstStarted.complete();
+        await firstCanFinish.future;
+      });
+
+      await firstStarted.future;
+      expect(controller.busy, isTrue);
+
+      final reentrant = await controller.run(() async {});
+      expect(reentrant, isFalse,
+          reason: 'second run while busy must be rejected without invoking callback');
+
+      firstCanFinish.complete();
+      expect(await firstFuture, isTrue);
+      expect(controller.busy, isFalse);
+    });
+
+    test('clearError resets error and notifies listeners', () async {
+      final controller = AsyncActionController();
+      addTearDown(controller.dispose);
+
+      var notifyCount = 0;
+      controller.addListener(() => notifyCount++);
+
+      await controller.run(() async => throw Exception('x'));
+      expect(controller.error, isNotNull);
+      final beforeClear = notifyCount;
+
+      controller.clearError();
+      expect(controller.error, isNull);
+      expect(notifyCount, beforeClear + 1);
+
+      // No-op when already cleared.
+      controller.clearError();
+      expect(notifyCount, beforeClear + 1);
+    });
+  });
+}