fix: 견적→수주 변환 시 담당자 정보 누락 수정

- Order::createFromQuote() 잘못된 필드명 수정 (contact_person→contact, delivery_date→completion_date)
- 견적 담당자(manager)를 orders.options.manager_name에 저장
- StoreOrderRequest/UpdateOrderRequest에 options.manager_name 유효성 검증 추가
- WorkOrderService show()에서 salesOrder.options 컬럼 포함하여 담당자 표시

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Services/WorkOrderService.php

@@ -210,7 +210,7 @@ public function show(int $id)
                 'assignee:id,name',
                 'assignees.user:id,name',
                 'team:id,name',
-                'salesOrder' => fn ($q) => $q->select('id', 'order_no', 'site_name', 'client_id', 'client_contact', 'received_at', 'writer_id', 'created_at', 'quantity')->withCount('rootNodes'),
+                'salesOrder' => fn ($q) => $q->select('id', 'order_no', 'site_name', 'client_id', 'client_contact', 'received_at', 'writer_id', 'created_at', 'quantity', 'options')->withCount('rootNodes'),
                 'salesOrder.client:id,name',
                 'salesOrder.writer:id,name',
                 'process:id,process_name,process_code,work_steps,department,options',