feat(flags): Feature-Flags aus Config-Datei; Gutschriften-Abschnitt abschaltbar

- Schalter stehen in assets/feature_flags.json (Key -> enabled +
  Beschreibung) statt als Konstanten im Code
- Enum Feature buendelt die stabilen Keys; FeatureFlags liest die Datei,
  ignoriert unbekannte Keys und nutzt fuer fehlende den Default aus dem Enum
- Laden beim App-Start im AppBloc, bereitgestellt per RepositoryProvider;
  FeatureGate blendet Bereiche bei inaktivem Feature komplett aus
- articles.credit_section = false: Abschnitt "Gutschriften" im
  Artikel-Step ist ausgeblendet
- Bisheriges Stepper-Flag migriert (articles.credit_amount_stepper); die
  fuenf ungenutzten statischen Flags mit veralteten Kommentaren entfernt
- Tests: Asset enthaelt alle Keys, Parsing, Defaults, FeatureGate

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/environment_settings_page_test.dart

@@ -10,6 +10,8 @@ import 'package:hl_lieferservice/bloc/app_states.dart';
 import 'package:hl_lieferservice/data/network/backend_config.dart';
 import 'package:hl_lieferservice/data/network/backend_environment.dart';
 import 'package:hl_lieferservice/data/network/environment_repository.dart';
+import 'package:hl_lieferservice/feature/feature_flags/feature_flags.dart';
+import 'package:hl_lieferservice/feature/feature_flags/feature_flags_repository.dart';
 import 'package:hl_lieferservice/feature/settings/presentation/environment_settings_page.dart';
 
 /// Liest die echte Asset-Config, speichert die Auswahl im Speicher.
@@ -31,6 +33,14 @@ class _FakeRepository extends EnvironmentRepository {
   Future<void> saveSelectedId(String id) async => selectedId = id;
 }
 
+/// Ohne Asset-Bundle: leere Schalter (alle Features auf ihrem Default).
+class _NoFlags extends FeatureFlagsRepository {
+  const _NoFlags();
+
+  @override
+  Future<FeatureFlags> load() async => const FeatureFlags({});
+}
+
 void main() {
   late _FakeRepository repo;
   late List<BackendConfig> activated;
@@ -39,15 +49,20 @@ void main() {
   setUp(() {
     repo = _FakeRepository(null);
     activated = [];
-    bloc = AppBloc(repository: repo, activate: activated.add);
+    bloc = AppBloc(
+      repository: repo,
+      activate: activated.add,
+      featureFlagsRepository: const _NoFlags(),
+    );
   });
 
   tearDown(() => bloc.close());
 
   test('ohne gespeicherte Wahl startet die Default-Umgebung', () async {
     bloc.add(AppLoadConfig(path: 'hl_server_config.json'));
-    final state = await bloc.stream.firstWhere((s) => s is AppConfigLoaded)
-        as AppConfigLoaded;
+    final state =
+        await bloc.stream.firstWhere((s) => s is AppConfigLoaded)
+            as AppConfigLoaded;
 
     expect(state.active.id, 'production');
     expect(activated.single.apiBaseUrl, 'http://192.168.1.9:3000');
@@ -56,14 +71,16 @@ void main() {
   test('gespeicherte, aber unbekannte Umgebung fällt auf Default', () async {
     repo.selectedId = 'gibt-es-nicht';
     bloc.add(AppLoadConfig(path: 'hl_server_config.json'));
-    final state = await bloc.stream.firstWhere((s) => s is AppConfigLoaded)
-        as AppConfigLoaded;
+    final state =
+        await bloc.stream.firstWhere((s) => s is AppConfigLoaded)
+            as AppConfigLoaded;
 
     expect(state.active.id, 'production');
   });
 
-  testWidgets('Card antippen wechselt Umgebung, speichert und schließt',
-      (tester) async {
+  testWidgets('Card antippen wechselt Umgebung, speichert und schließt', (
+    tester,
+  ) async {
     await tester.runAsync(() async {
       bloc.add(AppLoadConfig(path: 'hl_server_config.json'));
       await bloc.stream.firstWhere((s) => s is AppConfigLoaded);
@@ -74,16 +91,18 @@ void main() {
         value: bloc,
         child: MaterialApp(
           home: Builder(
-            builder: (context) => Scaffold(
-              body: TextButton(
-                onPressed: () => Navigator.of(context).push(
-                  MaterialPageRoute(
-                    builder: (_) => const EnvironmentSettingsPage(),
+            builder:
+                (context) => Scaffold(
+                  body: TextButton(
+                    onPressed:
+                        () => Navigator.of(context).push(
+                          MaterialPageRoute(
+                            builder: (_) => const EnvironmentSettingsPage(),
+                          ),
+                        ),
+                    child: const Text('open'),
                   ),
                 ),
-                child: const Text('open'),
-              ),
-            ),
           ),
         ),
       ),

test/feature_flags_test.dart

@@ -0,0 +1,86 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_bloc/flutter_bloc.dart';
+import 'package:flutter_test/flutter_test.dart';
+
+import 'package:hl_lieferservice/feature/feature_flags/feature.dart';
+import 'package:hl_lieferservice/feature/feature_flags/feature_flags.dart';
+import 'package:hl_lieferservice/feature/feature_flags/feature_gate.dart';
+
+Map<String, dynamic> _asset() =>
+    jsonDecode(File('assets/feature_flags.json').readAsStringSync())
+        as Map<String, dynamic>;
+
+void main() {
+  group('assets/feature_flags.json', () {
+    test('enthält jeden Feature-Key genau so, wie er im Code steht', () {
+      final keys = (_asset()['features'] as Map<String, dynamic>).keys.toSet();
+      for (final f in Feature.values) {
+        expect(keys, contains(f.key), reason: 'Key fehlt: ${f.key}');
+      }
+    });
+
+    test('Gutschriften-Abschnitt ist aktuell deaktiviert', () {
+      final flags = FeatureFlags.fromJson(_asset());
+      expect(flags.isEnabled(Feature.articlesCreditSection), isFalse);
+    });
+  });
+
+  group('FeatureFlags.fromJson', () {
+    test('fehlender Key fällt auf den Default zurück', () {
+      final flags = FeatureFlags.fromJson({'features': <String, dynamic>{}});
+      for (final f in Feature.values) {
+        expect(flags.isEnabled(f), f.defaultEnabled);
+      }
+    });
+
+    test('unbekannte Keys werden ignoriert', () {
+      final flags = FeatureFlags.fromJson({
+        'features': {
+          'gibt.es.nicht': {'enabled': true},
+          'articles.credit_section': {'enabled': false},
+        },
+      });
+      expect(flags.isEnabled(Feature.articlesCreditSection), isFalse);
+    });
+
+    test('kein bool bei enabled ist ein Fehler', () {
+      expect(
+        () => FeatureFlags.fromJson({
+          'features': {
+            'articles.credit_section': {'enabled': 'nein'},
+          },
+        }),
+        throwsFormatException,
+      );
+    });
+  });
+
+  group('FeatureGate', () {
+    Future<void> pumpGate(WidgetTester tester, {required bool enabled}) {
+      return tester.pumpWidget(
+        RepositoryProvider.value(
+          value: FeatureFlags({Feature.articlesCreditSection.key: enabled}),
+          child: const MaterialApp(
+            home: FeatureGate(
+              feature: Feature.articlesCreditSection,
+              child: Text('Gutschriften'),
+            ),
+          ),
+        ),
+      );
+    }
+
+    testWidgets('zeigt den Inhalt bei aktivem Feature', (tester) async {
+      await pumpGate(tester, enabled: true);
+      expect(find.text('Gutschriften'), findsOneWidget);
+    });
+
+    testWidgets('blendet den Inhalt bei inaktivem Feature aus', (tester) async {
+      await pumpGate(tester, enabled: false);
+      expect(find.text('Gutschriften'), findsNothing);
+    });
+  });
+}