Initial version

lib/services/pin_store.dart

@@ -0,0 +1,28 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+/// Remembers scooter PINs in platform secure storage (Android Keystore backed
+/// storage, iOS Keychain), keyed by the BLE peripheral id.
+///
+/// The peripheral id is not a permanent scooter identity (see ScooterDevice).
+/// Once the Apollo UID is read over AT+UID? this should key by that instead.
+class PinStore {
+  PinStore([FlutterSecureStorage? storage])
+      : _storage = storage ?? const FlutterSecureStorage();
+
+  final FlutterSecureStorage _storage;
+
+  String _key(String deviceId) => 'pin:$deviceId';
+
+  Future<String?> read(String deviceId) async {
+    try {
+      return await _storage.read(key: _key(deviceId));
+    } catch (_) {
+      return null;
+    }
+  }
+
+  Future<void> save(String deviceId, String pin) =>
+      _storage.write(key: _key(deviceId), value: pin);
+
+  Future<void> forget(String deviceId) => _storage.delete(key: _key(deviceId));
+}