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/Http/Requests/V1/Receiving/StoreReceivingRequest.php

@@ -24,6 +24,9 @@ public function rules(): array
             'order_qty' => ['nullable', 'numeric', 'min:0'],
             'order_unit' => ['nullable', 'string', 'max:20'],
             'due_date' => ['nullable', 'date'],
+            'receiving_qty' => ['nullable', 'numeric', 'min:0'],
+            'receiving_date' => ['nullable', 'date'],
+            'lot_no' => ['nullable', 'string', 'max:50'],
             'status' => ['nullable', 'string', 'in:order_completed,shipping,inspection_pending,receiving_pending'],
             'remark' => ['nullable', 'string', 'max:1000'],
         ];