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/query.go

@@ -233,7 +233,7 @@ func (r *Repository) baseQuery(ctx context.Context) *gorm.DB {
 				WHEN lu.id IS NULL THEN ?
 				WHEN COALESCE(lu.source_channel, '') = '' THEN ?
 				ELSE lu.source_channel
-			END AS source_channel`, sourceChannelWebsite, sourceChannelExternalUnknown).
+			END AS display_source_channel`, sourceChannelWebsite, sourceChannelExternalUnknown).
 		Joins("JOIN game_accounts AS a ON a.id = l.account_id").
 		Joins("LEFT JOIN users AS u ON u.id = l.owner_id").
 		Joins("LEFT JOIN distribution_sites AS src_site ON src_site.id = l.distribution_site_id").