fix: [입고] order_qty validation을 required로 변경하여 SQL 에러 대신 명확한 안내 반환

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

@@ -21,7 +21,7 @@ public function rules(): array
             'item_name' => ['required', 'string', 'max:200'],
             'specification' => ['nullable', 'string', 'max:200'],
             'supplier' => ['required', 'string', 'max:100'],
-            'order_qty' => ['nullable', 'numeric', 'min:0'],
+            'order_qty' => ['required', 'numeric', 'min:0.01'],
             'order_unit' => ['nullable', 'string', 'max:20'],
             'due_date' => ['nullable', 'date'],
             'receiving_qty' => ['nullable', 'numeric', 'min:0'],