major refactor

lib/services/token_storage_service.dart

@@ -0,0 +1,57 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+/// Stores the auth token in secure storage and falls back to SharedPreferences
+/// so debug builds and platforms without a working keyring still persist.
+class TokenStorageService {
+  TokenStorageService._internal();
+
+  static final TokenStorageService _instance = TokenStorageService._internal();
+
+  factory TokenStorageService() => _instance;
+
+  static const _tokenKey = 'auth_token';
+  final FlutterSecureStorage _secureStorage = const FlutterSecureStorage();
+
+  Future<SharedPreferences> get _prefs async =>
+      await SharedPreferences.getInstance();
+
+  Future<void> setToken(String token) async {
+    try {
+      await _secureStorage.write(key: _tokenKey, value: token);
+    } catch (_) {
+      // ignore secure storage failures in debug/unsupported environments
+    }
+    final prefs = await _prefs;
+    await prefs.setString(_tokenKey, token);
+  }
+
+  Future<String?> getToken() async {
+    try {
+      final secured = await _secureStorage.read(key: _tokenKey);
+      if (secured != null && secured.isNotEmpty) {
+        return secured;
+      }
+    } catch (_) {
+      // ignore and fall back
+    }
+    final prefs = await _prefs;
+    final token = prefs.getString(_tokenKey);
+    return (token == null || token.isEmpty) ? null : token;
+  }
+
+  Future<void> clearToken() async {
+    try {
+      await _secureStorage.delete(key: _tokenKey);
+    } catch (_) {
+      // ignore
+    }
+    final prefs = await _prefs;
+    await prefs.remove(_tokenKey);
+  }
+
+  Future<bool> hasToken() async {
+    final token = await getToken();
+    return token != null && token.isNotEmpty;
+  }
+}