refactor: clean up imports in api_client and auth_repository files

flutter/lib/core/api/api_client.dart

@@ -1,4 +1,3 @@
-import 'dart:io';
 import 'package:http/http.dart' as http;
 
 /// Platform-neutral HTTP client wrapping the internal API base URL.

flutter/lib/features/auth/data/auth_repository.dart

@@ -1,6 +1,6 @@
 import 'dart:convert';
-import '../../core/api/api_client.dart';
-import '../../core/platform/token_storage.dart';
+import '../../../core/api/api_client.dart';
+import '../../../core/platform/token_storage.dart';
 
 class AuthRepository {
   final ApiClient _api;

flutter/pubspec.yaml

@@ -16,7 +16,6 @@ dependencies:
   flutter_riverpod: ^2.5.1
   http: ^1.2.1
   shared_preferences: ^2.2.3
-  flutter_secure_storage: ^9.2.2
 
 dev_dependencies:
   flutter_test: