persist twoPageMode

lib/storage_helper.dart

@@ -3,8 +3,21 @@ import 'package:hive/hive.dart';
 
 enum SecureStorageKey { url, jwt, email, password }
 
+enum ConfigKey { twoPageMode }
+
+class Config {
+  Config({required this.twoPageMode, required this.fullscreen});
+
+  static const String keyTwoPageMode = "twoPageMode";
+  static const String keyFullscreen = "fullscreen";
+
+  bool twoPageMode;
+  bool fullscreen;
+}
+
 class StorageHelper {
   final sheetAccessTimesBox = "sheetAccessTimes";
+  final configBox = "config";
 
   late FlutterSecureStorage secureStorage;
 
@@ -22,6 +35,20 @@ class StorageHelper {
     return secureStorage.write(key: key.name, value: value);
   }
 
+  Future<Config> readConfig() async {
+    final box = await Hive.openBox(configBox);
+    return Config(
+      twoPageMode: box.get(Config.keyTwoPageMode) ?? false,
+      fullscreen: box.get(Config.keyFullscreen) ?? false,
+    );
+  }
+
+  Future<void> writeConfig(Config config) async {
+    final box = await Hive.openBox(configBox);
+    box.put(Config.keyTwoPageMode, config.twoPageMode);
+    box.put(Config.keyFullscreen, config.fullscreen);
+  }
+
   Future<Map<String, DateTime>> readSheetAccessTimes() async {
     final box = await Hive.openBox(sheetAccessTimesBox);
     return box.toMap().map(