결재 템플릿 단계 적용 구현

- ApprovalTemplate 엔티티·DTO·원격 리포지토리 추가
- ApprovalController에 템플릿 로딩/적용 상태와 assignSteps 호출 연동
- ApprovalPage 단계 탭에 템플릿 선택 UI 및 적용 확인 다이얼로그 구현
- 템플릿 적용 단위 테스트와 IMPLEMENTATION_TASKS 현황 갱신

lib/features/masters/group/data/dtos/group_dto.dart

@@ -6,6 +6,7 @@ class GroupDto {
   GroupDto({
     this.id,
     required this.groupName,
+    this.description,
     this.isDefault = false,
     this.isActive = true,
     this.isDeleted = false,
@@ -16,6 +17,7 @@ class GroupDto {
 
   final int? id;
   final String groupName;
+  final String? description;
   final bool isDefault;
   final bool isActive;
   final bool isDeleted;
@@ -27,6 +29,7 @@ class GroupDto {
     return GroupDto(
       id: json['id'] as int?,
       groupName: json['group_name'] as String,
+      description: json['description'] as String?,
       isDefault: (json['is_default'] as bool?) ?? false,
       isActive: (json['is_active'] as bool?) ?? true,
       isDeleted: (json['is_deleted'] as bool?) ?? false,
@@ -39,6 +42,7 @@ class GroupDto {
   Group toEntity() => Group(
     id: id,
     groupName: groupName,
+    description: description,
     isDefault: isDefault,
     isActive: isActive,
     isDeleted: isDeleted,