fix(WEB): 입고 등록 검증 실패 수정 - Store 규칙 보완 및 상태값 정합성

- StoreReceivingRequest에 receiving_qty, receiving_date, lot_no 규칙 추가
- UpdateReceivingRequest status에 inspection_completed 허용 추가
- ReceivingService store()에 receiving_qty/date/lot_no 저장 처리
- order_qty null 안전 처리, 기본 status를 receiving_pending으로 변경

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

app/Services/ReceivingService.php

@@ -194,10 +194,13 @@ public function store(array $data): Receiving
             $receiving->item_name = $data['item_name'];
             $receiving->specification = $data['specification'] ?? null;
             $receiving->supplier = $data['supplier'];
-            $receiving->order_qty = $data['order_qty'];
+            $receiving->order_qty = $data['order_qty'] ?? null;
             $receiving->order_unit = $data['order_unit'] ?? 'EA';
             $receiving->due_date = $data['due_date'] ?? null;
-            $receiving->status = $data['status'] ?? 'order_completed';
+            $receiving->receiving_qty = $data['receiving_qty'] ?? null;
+            $receiving->receiving_date = $data['receiving_date'] ?? null;
+            $receiving->lot_no = $data['lot_no'] ?? null;
+            $receiving->status = $data['status'] ?? 'receiving_pending';
             $receiving->remark = $data['remark'] ?? null;
 
             // options 필드 처리 (제조사, 수입검사 등 확장 필드)