feat(API): Model 및 관계 추가

- HandoverReport, HandoverReportItem, HandoverReportManager 모델 추가
- SiteBriefing 모델 추가
- StructureReview, FcmSendLog, Position, Salary 수정
- Order 모델 정리

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

app/Models/Orders/Order.php

@@ -2,7 +2,6 @@
 
 namespace App\Models\Orders;
 
-use App\Models\Clients\Client;
 use App\Models\Items\Item;
 use App\Models\Quote\Quote;
 use App\Traits\BelongsToTenant;