fix: задание от стасика

lib/core/config/app_show_extra_info.dart

@@ -0,0 +1,20 @@
+import 'package:flutter/foundation.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+class AppShowExtraInfo {
+  static const prefKey = 'dev_show_extra_info';
+  static const bool defaultValue = false;
+
+  static final ValueNotifier<bool> current = ValueNotifier(defaultValue);
+
+  static Future<bool> load() async {
+    final prefs = await SharedPreferences.getInstance();
+    return prefs.getBool(prefKey) ?? defaultValue;
+  }
+
+  static Future<void> save(bool value) async {
+    current.value = value;
+    final prefs = await SharedPreferences.getInstance();
+    await prefs.setBool(prefKey, value);
+  }
+}