fix(distribution): 修正商品归属回填、禁止全站灌货并拒绝无效站点头

用货架写入时间与上传来源回滚误标产地，不再依赖绝对时间戳；同步仅收本站上传与显式勾选。

backend/internal/modules/listing/mutation.go

@@ -22,6 +22,22 @@ func (r *Repository) Create(ctx context.Context, ownerID uint64, req CreateReque
 		if err := r.ensureCreateCooldown(tx, ownerID, publishCooldown, now); err != nil {
 			return err
 		}
+
+		var site model.DistributionSite
+		var siteID *uint64
+		originChannel := ""
+		if len(siteCode) > 0 && strings.TrimSpace(siteCode[0]) != "" {
+			trimmedSiteCode := strings.TrimSpace(siteCode[0])
+			if err := tx.Where("site_code = ? AND status = 'active'", trimmedSiteCode).First(&site).Error; err != nil {
+				if errors.Is(err, gorm.ErrRecordNotFound) {
+					return ErrDistributionSiteInvalid
+				}
+				return err
+			}
+			siteID = &site.ID
+			originChannel = site.SiteCode
+		}
+
 		listingNo, err := r.nextListingNo(tx, now)
 		if err != nil {
 			return err
@@ -35,6 +51,7 @@ func (r *Repository) Create(ctx context.Context, ownerID uint64, req CreateReque
 			return err
 		}
 		listingStatus, reviewStatus, publishedAt := initialPublishState(reviewRequired)
+
 		account := model.GameAccount{
 			OwnerID:        ownerID,
 			GameName:       "delta_force",
@@ -52,15 +69,6 @@ func (r *Repository) Create(ctx context.Context, ownerID uint64, req CreateReque
 			return err
 		}
 
-		var site model.DistributionSite
-		var siteID *uint64
-		if len(siteCode) > 0 && strings.TrimSpace(siteCode[0]) != "" {
-			trimmedSiteCode := strings.TrimSpace(siteCode[0])
-			if err := tx.Where("site_code = ? AND status = 'active'", trimmedSiteCode).First(&site).Error; err == nil {
-				siteID = &site.ID
-			}
-		}
-
 		priceCent := normalizedListingPriceCent(req)
 		listing := model.RentalListing{
 			ListingNo:          listingNo,
@@ -72,6 +80,7 @@ func (r *Repository) Create(ctx context.Context, ownerID uint64, req CreateReque
 			ReviewStatus:       reviewStatus,
 			PublishedAt:        publishedAt,
 			DistributionSiteID: siteID,
+			SourceChannel:      originChannel,
 		}
 		if err := tx.Create(&listing).Error; err != nil {
 			return err
@@ -203,6 +212,7 @@ func (r *Repository) CreateFromExternalUpload(ctx context.Context, upload extern
 			HandoffMode:       "platform",
 			SettlementMode:    "platform_managed",
 			ManagedAdminID:    &admin.ID,
+			SourceChannel:     upload.SourceChannel,
 		}
 		if err := tx.Create(&listing).Error; err != nil {
 			return err