fix: 修复平台自营资源（未分配代理）无法线下下单的问题

offline 支付分支新增平台自营子场景判断：
- 资源 shopID 为空时（未分配给任何代理商），使用零售价直接创建订单
- 资源 shopID 不为空时（属于代理商），走原有平台代购逻辑

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

internal/service/order/service.go

@@ -398,25 +398,44 @@ func (s *Service) CreateAdminOrder(ctx context.Context, req *dto.CreateAdminOrde
 
 	// 根据支付方式分别处理
 	if req.PaymentMethod == model.PaymentMethodOffline {
-		// ==== 场景 1：平台代购（offline）====
+		// ==== 场景 1：offline（线下支付）====
-		purchaseBuyerID, buyerCostPrice, purchasePaidAt, err := s.resolvePurchaseOnBehalfInfo(ctx, validationResult)
+		isPlatformOwned := resourceShopID == nil || *resourceShopID == 0
-		if err != nil {
-			return nil, err
-		}
-		orderBuyerType = model.BuyerTypeAgent
-		orderBuyerID = purchaseBuyerID
-		totalAmount = buyerCostPrice
-		paymentMethod = model.PaymentMethodOffline
-		paymentStatus = model.PaymentStatusPaid
-		paidAt = purchasePaidAt
-		isPurchaseOnBehalf = true
-		sellerCostPrice = buyerCostPrice
 
-		// 设置操作者信息（平台代购）
+		if isPlatformOwned {
-		operatorID = nil
+			// ==== 子场景 1.1：平台自营（资源未分配给代理商）====
-		operatorType = constants.OwnerTypePlatform
+			// 平台直接销售给终端用户，无代理商参与，使用零售价，无需查询分配配置
-		purchaseRole = model.PurchaseRolePurchasedByPlatform
+			orderBuyerType = model.BuyerTypePersonal
-		actualPaidAmount = nil
+			orderBuyerID = 0
+			paymentMethod = model.PaymentMethodOffline
+			paymentStatus = model.PaymentStatusPaid
+			paidAt = &now
+			isPurchaseOnBehalf = false
+			sellerCostPrice = 0
+			operatorID = nil
+			operatorType = constants.OwnerTypePlatform
+			purchaseRole = model.PurchaseRoleSelfPurchase
+			actualPaidAmount = nil
+		} else {
+			// ==== 子场景 1.2：平台代购（资源属于代理商，平台代为购买）====
+			purchaseBuyerID, buyerCostPrice, purchasePaidAt, err := s.resolvePurchaseOnBehalfInfo(ctx, validationResult)
+			if err != nil {
+				return nil, err
+			}
+			orderBuyerType = model.BuyerTypeAgent
+			orderBuyerID = purchaseBuyerID
+			totalAmount = buyerCostPrice
+			paymentMethod = model.PaymentMethodOffline
+			paymentStatus = model.PaymentStatusPaid
+			paidAt = purchasePaidAt
+			isPurchaseOnBehalf = true
+			sellerCostPrice = buyerCostPrice
+
+			// 设置操作者信息（平台代购）
+			operatorID = nil
+			operatorType = constants.OwnerTypePlatform
+			purchaseRole = model.PurchaseRolePurchasedByPlatform
+			actualPaidAmount = nil
+		}
 
 	} else if req.PaymentMethod == model.PaymentMethodWallet {
 		// ==== 场景 2：代理钱包支付（wallet）====