added app settings api

lib/service/storage.dart

@@ -4,22 +4,46 @@ import 'package:shared_preferences/shared_preferences.dart';
 
 import '../model/bookmark.dart';
 import '../model/collection.dart';
+import '../model/settings.dart';
 import 'json_file_service.dart';
 
 class Storage {
   static const String _bookmarksKey = 'bookmarks';
   static const String _collectionsKey = 'collections';
   static SharedPreferencesWithCache? _prefsWithCache;
+  static const String _settingsKey = 'settings';
   static const String _statsKey = 'stats';
 
   static Future<void> initialize() async {
     _prefsWithCache = await SharedPreferencesWithCache.create(
       cacheOptions: const SharedPreferencesWithCacheOptions(
-        allowList: <String>{_collectionsKey, _bookmarksKey, _statsKey},
+        allowList: <String>{
+          _collectionsKey,
+          _bookmarksKey,
+          _statsKey,
+          _settingsKey,
+        },
       ),
     );
   }
 
+  static Settings loadSettings() {
+    final jsonString = _prefs.getString(_settingsKey);
+    if (jsonString != null) {
+      final json = jsonDecode(jsonString) as Map<String, dynamic>;
+      return Settings.fromJson(json);
+    } else {
+      final settings = Settings.defaults();
+      saveSettings(settings);
+      return settings;
+    }
+  }
+
+  static Future<void> saveSettings(Settings settings) {
+    final json = jsonEncode(settings.toJson());
+    return _prefs.setString(_settingsKey, json);
+  }
+
   static List<Collection> loadCollections() {
     final jsonString = _prefs.getString(_collectionsKey) ?? '[]';
     final jsonList = jsonDecode(jsonString) as List;
@@ -156,15 +180,6 @@ class Storage {
     await _prefs.setString(_statsKey, jsonEncode(stats));
   }
 
-  static SharedPreferencesWithCache get _prefs {
-    if (_prefsWithCache == null) {
-      throw StateError(
-        'BookmarkStorage not initialized. Call initialize() first.',
-      );
-    }
-    return _prefsWithCache!;
-  }
-
   static Future<bool> exportToJsonFile() => JsonFileService.exportToJson(
     collections: loadCollections(),
     bookmarks: loadBookmarks(),
@@ -180,4 +195,13 @@ class Storage {
     }
     return false;
   }
+
+  static SharedPreferencesWithCache get _prefs {
+    if (_prefsWithCache == null) {
+      throw StateError(
+        'BookmarkStorage not initialized. Call initialize() first.',
+      );
+    }
+    return _prefsWithCache!;
+  }
 }