feat(07-02): build SortDropdown widget and integrate into HomeScreen and TaskListScreen

- Create SortDropdown ConsumerWidget using PopupMenuButton<TaskSortOption>
- Displays current sort label with sort icon in AppBar actions
- Check mark shown on active option via Opacity widget
- Add Scaffold with AppBar (title: Übersicht, actions: SortDropdown) to HomeScreen
- Add SortDropdown before edit/delete IconButtons in TaskListScreen AppBar

lib/features/tasks/presentation/sort_dropdown.dart

@@ -0,0 +1,71 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import 'package:household_keeper/features/tasks/domain/task_sort_option.dart';
+import 'package:household_keeper/features/tasks/presentation/sort_preference_notifier.dart';
+import 'package:household_keeper/l10n/app_localizations.dart';
+
+/// A reusable sort dropdown widget for use in AppBar actions.
+///
+/// Displays the current sort option as a labelled button with a sort icon.
+/// Tapping opens a popup menu with three options: A–Z, Intervall, Aufwand.
+/// The active option is indicated with a visible check mark.
+///
+/// Reads sort state from [sortPreferenceProvider] and writes via
+/// [SortPreferenceNotifier.setSortOption].
+class SortDropdown extends ConsumerWidget {
+  const SortDropdown({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final current = ref.watch(sortPreferenceProvider);
+    final l10n = AppLocalizations.of(context);
+    final theme = Theme.of(context);
+
+    return PopupMenuButton<TaskSortOption>(
+      onSelected: (value) =>
+          ref.read(sortPreferenceProvider.notifier).setSortOption(value),
+      itemBuilder: (context) => TaskSortOption.values.map((option) {
+        final isSelected = option == current;
+        return PopupMenuItem<TaskSortOption>(
+          value: option,
+          child: Row(
+            children: [
+              Opacity(
+                opacity: isSelected ? 1.0 : 0.0,
+                child: const Icon(Icons.check, size: 18),
+              ),
+              const SizedBox(width: 8),
+              Text(_label(option, l10n)),
+            ],
+          ),
+        );
+      }).toList(),
+      child: Padding(
+        padding: const EdgeInsets.symmetric(horizontal: 8),
+        child: Row(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            const Icon(Icons.sort),
+            const SizedBox(width: 4),
+            Text(
+              _label(current, l10n),
+              style: theme.textTheme.labelLarge,
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+
+  String _label(TaskSortOption option, AppLocalizations l10n) {
+    switch (option) {
+      case TaskSortOption.alphabetical:
+        return l10n.sortAlphabetical;
+      case TaskSortOption.interval:
+        return l10n.sortInterval;
+      case TaskSortOption.effort:
+        return l10n.sortEffort;
+    }
+  }
+}

lib/features/tasks/presentation/task_list_screen.dart

@@ -4,6 +4,7 @@ import 'package:go_router/go_router.dart';
 
 import 'package:household_keeper/core/database/database.dart';
 import 'package:household_keeper/core/providers/database_provider.dart';
+import 'package:household_keeper/features/tasks/presentation/sort_dropdown.dart';
 import 'package:household_keeper/features/tasks/presentation/task_providers.dart';
 import 'package:household_keeper/features/tasks/presentation/task_row.dart';
 import 'package:household_keeper/l10n/app_localizations.dart';
@@ -27,6 +28,7 @@ class TaskListScreen extends ConsumerWidget {
       appBar: AppBar(
         title: _RoomTitle(roomId: roomId),
         actions: [
+          const SortDropdown(),
           IconButton(
             icon: const Icon(Icons.edit),
             onPressed: () => context.go('/rooms/$roomId/edit'),