test: 통합 테스트 오류 및 경고 수정

- 모든 서비스 메서드 시그니처를 실제 구현에 맞게 수정
- TestDataGenerator 제거하고 직접 객체 생성으로 변경
- 모델 필드명 및 타입 불일치 수정
- 불필요한 Either 패턴 사용 제거
- null safety 관련 이슈 해결

수정된 파일:
- test/integration/screens/company_integration_test.dart
- test/integration/screens/equipment_integration_test.dart
- test/integration/screens/user_integration_test.dart
- test/integration/screens/login_integration_test.dart

test/integration/mock/mock_secure_storage.dart

@@ -0,0 +1,93 @@
+import 'package:flutter_secure_storage/flutter_secure_storage.dart';
+
+/// 테스트를 위한 Mock SecureStorage
+class MockSecureStorage extends FlutterSecureStorage {
+  final Map<String, String> _storage = {};
+  
+  @override
+  Future<void> write({
+    required String key,
+    required String? value,
+    IOSOptions? iOptions,
+    AndroidOptions? aOptions,
+    LinuxOptions? lOptions,
+    WebOptions? webOptions,
+    MacOsOptions? mOptions,
+    WindowsOptions? wOptions,
+  }) async {
+    if (value != null) {
+      _storage[key] = value;
+      // 디버깅용 print문 제거
+    }
+  }
+  
+  @override
+  Future<String?> read({
+    required String key,
+    IOSOptions? iOptions,
+    AndroidOptions? aOptions,
+    LinuxOptions? lOptions,
+    WebOptions? webOptions,
+    MacOsOptions? mOptions,
+    WindowsOptions? wOptions,
+  }) async {
+    final value = _storage[key];
+    // 디버깅용 print문 제거
+    return value;
+  }
+  
+  @override
+  Future<void> delete({
+    required String key,
+    IOSOptions? iOptions,
+    AndroidOptions? aOptions,
+    LinuxOptions? lOptions,
+    WebOptions? webOptions,
+    MacOsOptions? mOptions,
+    WindowsOptions? wOptions,
+  }) async {
+    _storage.remove(key);
+    // 디버깅용 print문 제거
+  }
+  
+  @override
+  Future<void> deleteAll({
+    IOSOptions? iOptions,
+    AndroidOptions? aOptions,
+    LinuxOptions? lOptions,
+    WebOptions? webOptions,
+    MacOsOptions? mOptions,
+    WindowsOptions? wOptions,
+  }) async {
+    _storage.clear();
+    // 디버깅용 print문 제거
+  }
+  
+  @override
+  Future<Map<String, String>> readAll({
+    IOSOptions? iOptions,
+    AndroidOptions? aOptions,
+    LinuxOptions? lOptions,
+    WebOptions? webOptions,
+    MacOsOptions? mOptions,
+    WindowsOptions? wOptions,
+  }) async {
+    // 디버깅용 print문 제거
+    return Map<String, String>.from(_storage);
+  }
+  
+  @override
+  Future<bool> containsKey({
+    required String key,
+    IOSOptions? iOptions,
+    AndroidOptions? aOptions,
+    LinuxOptions? lOptions,
+    WebOptions? webOptions,
+    MacOsOptions? mOptions,
+    WindowsOptions? wOptions,
+  }) async {
+    final contains = _storage.containsKey(key);
+    // 디버깅용 print문 제거
+    return contains;
+  }
+}