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/Tenants/Position.php

@@ -74,4 +74,4 @@ public function scopeOrdered($query)
     {
         return $query->orderBy('sort_order');
     }
-}
+}