승인 단계 삭제 복구 흐름 구현하고 API 정렬 문서 추가

lib/features/approvals/domain/entities/approval.dart

@@ -103,6 +103,7 @@ class ApprovalStep {
     required this.assignedAt,
     this.decidedAt,
     this.note,
+    this.isDeleted = false,
   });
 
   final int? id;
@@ -112,6 +113,29 @@ class ApprovalStep {
   final DateTime assignedAt;
   final DateTime? decidedAt;
   final String? note;
+  final bool isDeleted;
+
+  ApprovalStep copyWith({
+    int? id,
+    int? stepOrder,
+    ApprovalApprover? approver,
+    ApprovalStatus? status,
+    DateTime? assignedAt,
+    DateTime? decidedAt,
+    String? note,
+    bool? isDeleted,
+  }) {
+    return ApprovalStep(
+      id: id ?? this.id,
+      stepOrder: stepOrder ?? this.stepOrder,
+      approver: approver ?? this.approver,
+      status: status ?? this.status,
+      assignedAt: assignedAt ?? this.assignedAt,
+      decidedAt: decidedAt ?? this.decidedAt,
+      note: note ?? this.note,
+      isDeleted: isDeleted ?? this.isDeleted,
+    );
+  }
 }
 
 class ApprovalApprover {