remove voice code make optimizations. Fix channels race conditions. add reply function

lib/storage/prefs_manager.dart

@@ -0,0 +1,33 @@
+import 'package:shared_preferences/shared_preferences.dart';
+
+/// Singleton wrapper for SharedPreferences to avoid redundant getInstance() calls.
+///
+/// BEFORE: Every storage operation called SharedPreferences.getInstance()
+/// AFTER: Single getInstance() on app startup, reused throughout lifecycle
+///
+/// This eliminates 30+ redundant platform channel calls across the app.
+class PrefsManager {
+  PrefsManager._();
+
+  static SharedPreferences? _instance;
+
+  /// Initialize the cached instance. Call this once during app startup in main().
+  static Future<void> initialize() async {
+    _instance ??= await SharedPreferences.getInstance();
+  }
+
+  /// Get the cached SharedPreferences instance.
+  /// Throws StateError if initialize() hasn't been called.
+  static SharedPreferences get instance {
+    if (_instance == null) {
+      throw StateError(
+          'PrefsManager not initialized. Call PrefsManager.initialize() in main() before use.');
+    }
+    return _instance!;
+  }
+
+  /// For testing: reset the instance
+  static void reset() {
+    _instance = null;
+  }
+}