fix(API): 입고 수정 시 completed 상태 변경 지원

- UpdateReceivingRequest: status 허용값에 completed 추가, receiving_qty/receiving_date/lot_no 필드 추가
- ReceivingService::update(): status가 completed로 변경 시 LOT번호 자동생성, 입고수량/입고일 설정, 재고 연동(StockService) 처리

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/Http/Requests/V1/Receiving/UpdateReceivingRequest.php

@@ -23,8 +23,11 @@ public function rules(): array
             'order_qty' => ['sometimes', 'numeric', 'min:0'],
             'order_unit' => ['nullable', 'string', 'max:20'],
             'due_date' => ['nullable', 'date'],
-            'status' => ['sometimes', 'string', 'in:order_completed,shipping,inspection_pending,receiving_pending'],
+            'status' => ['sometimes', 'string', 'in:order_completed,shipping,inspection_pending,receiving_pending,completed'],
             'remark' => ['nullable', 'string', 'max:1000'],
+            'receiving_qty' => ['nullable', 'numeric', 'min:0'],
+            'receiving_date' => ['nullable', 'date'],
+            'lot_no' => ['nullable', 'string', 'max:50'],
         ];
     }