feat: align shared app foundations

lib/common/storage/storage_service.dart

@@ -6,6 +6,8 @@ class StorageService {
   static StorageService? _instance;
   static StorageService get to => _instance!;
 
+  SharedPreferences get preferences => _prefs;
+
   static Future<StorageService> get instance async {
     if (_instance != null) return _instance!;
     final prefs = await SharedPreferences.getInstance();
@@ -17,4 +19,6 @@ class StorageService {
   Future<void> setBool(String key, bool v) => _prefs.setBool(key, v);
   String? getString(String key) => _prefs.getString(key);
   Future<void> setString(String key, String v) => _prefs.setString(key, v);
+  bool containsKey(String key) => _prefs.containsKey(key);
+  Future<void> remove(String key) => _prefs.remove(key);
 }