feat: 라이선스 관리 기능 개선 및 폼 검증 강화

- LicenseDto 모델 업데이트
- 라이선스 폼 UI 개선 및 검증 로직 강화
- 라이선스 리스트 화면 필터링 기능 추가
- 만료일 관리 기능 개선

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/data/models/license/license_dto.g.dart

@@ -16,7 +16,7 @@ _$LicenseDtoImpl _$$LicenseDtoImplFromJson(Map<String, dynamic> json) =>
       userCount: (json['user_count'] as num?)?.toInt(),
       purchaseDate: _dateFromJson(json['purchase_date'] as String?),
       expiryDate: _dateFromJson(json['expiry_date'] as String?),
-      purchasePrice: (json['purchase_price'] as num?)?.toDouble(),
+      purchasePrice: _priceFromJson(json['purchase_price']),
       companyId: (json['company_id'] as num?)?.toInt(),
       branchId: (json['branch_id'] as num?)?.toInt(),
       assignedUserId: (json['assigned_user_id'] as num?)?.toInt(),
@@ -39,7 +39,7 @@ Map<String, dynamic> _$$LicenseDtoImplToJson(_$LicenseDtoImpl instance) =>
       'user_count': instance.userCount,
       'purchase_date': _dateToJson(instance.purchaseDate),
       'expiry_date': _dateToJson(instance.expiryDate),
-      'purchase_price': instance.purchasePrice,
+      'purchase_price': _priceToJson(instance.purchasePrice),
       'company_id': instance.companyId,
       'branch_id': instance.branchId,
       'assigned_user_id': instance.assignedUserId,