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

lib/data/models/equipment/equipment_dto.g.dart

@@ -0,0 +1,61 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'equipment_dto.dart';
+
+// **************************************************************************
+// JsonSerializableGenerator
+// **************************************************************************
+
+_$EquipmentDtoImpl _$$EquipmentDtoImplFromJson(Map<String, dynamic> json) =>
+    _$EquipmentDtoImpl(
+      id: (json['id'] as num).toInt(),
+      serialNumber: json['serial_number'] as String,
+      name: json['name'] as String,
+      category: json['category'] as String?,
+      manufacturer: json['manufacturer'] as String?,
+      model: json['model'] as String?,
+      status: json['status'] as String,
+      companyId: (json['company_id'] as num).toInt(),
+      companyName: json['company_name'] as String?,
+      warehouseLocationId: (json['warehouse_location_id'] as num?)?.toInt(),
+      warehouseName: json['warehouse_name'] as String?,
+      purchaseDate: json['purchase_date'] as String?,
+      purchasePrice: (json['purchase_price'] as num?)?.toDouble(),
+      currentValue: (json['current_value'] as num?)?.toDouble(),
+      warrantyExpiry: json['warranty_expiry'] as String?,
+      lastMaintenanceDate: json['last_maintenance_date'] as String?,
+      nextMaintenanceDate: json['next_maintenance_date'] as String?,
+      specifications: json['specifications'] as Map<String, dynamic>?,
+      notes: json['notes'] as String?,
+      createdAt: json['created_at'] == null
+          ? null
+          : DateTime.parse(json['created_at'] as String),
+      updatedAt: json['updated_at'] == null
+          ? null
+          : DateTime.parse(json['updated_at'] as String),
+    );
+
+Map<String, dynamic> _$$EquipmentDtoImplToJson(_$EquipmentDtoImpl instance) =>
+    <String, dynamic>{
+      'id': instance.id,
+      'serial_number': instance.serialNumber,
+      'name': instance.name,
+      'category': instance.category,
+      'manufacturer': instance.manufacturer,
+      'model': instance.model,
+      'status': instance.status,
+      'company_id': instance.companyId,
+      'company_name': instance.companyName,
+      'warehouse_location_id': instance.warehouseLocationId,
+      'warehouse_name': instance.warehouseName,
+      'purchase_date': instance.purchaseDate,
+      'purchase_price': instance.purchasePrice,
+      'current_value': instance.currentValue,
+      'warranty_expiry': instance.warrantyExpiry,
+      'last_maintenance_date': instance.lastMaintenanceDate,
+      'next_maintenance_date': instance.nextMaintenanceDate,
+      'specifications': instance.specifications,
+      'notes': instance.notes,
+      'created_at': instance.createdAt?.toIso8601String(),
+      'updated_at': instance.updatedAt?.toIso8601String(),
+    };