feat(API): 부실채권, 재고, 입고 기능 개선

- BadDebt 컨트롤러/서비스 기능 확장
- StockService 재고 조회 로직 개선
- ProcessReceivingRequest 검증 규칙 수정
- Item, Order, CommonCode, Shipment 모델 업데이트
- TodayIssueObserverService 개선

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

app/Models/Tenants/Shipment.php

@@ -4,6 +4,7 @@
 
 use App\Models\Orders\Order;
 use App\Models\Production\WorkOrder;
+use App\Models\Products\CommonCode;
 use App\Traits\BelongsToTenant;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
@@ -77,6 +78,7 @@ class Shipment extends Model
      */
     protected $appends = [
         'order_info',
+        'delivery_method_label',
     ];
 
     /**
@@ -172,11 +174,11 @@ public function getPriorityLabelAttribute(): string
     }
 
     /**
-     * 배송방식 라벨
+     * 배송방식 라벨 (common_codes 테이블에서 조회)
      */
     public function getDeliveryMethodLabelAttribute(): string
     {
-        return self::DELIVERY_METHODS[$this->delivery_method] ?? $this->delivery_method;
+        return CommonCode::getLabel('delivery_method', $this->delivery_method);
     }
 
     /**