fix(distribution): 货架加价打通前台、下单与卖方分成

分站公开列表和详情展示当前货架加价；下单写入 base_price / shelf_markup / markup_site_id 快照并计入实付。
支付分账改用快照加价，不再误用 PlatformFeeCent；结账不退加价，事后改价不影响历史订单。

backend/internal/modules/listing/public_query.go

@@ -31,6 +31,9 @@ func (r *Repository) ListPublic(ctx context.Context, query PublicListQuery) (*Pu
 		return nil, err
 	}
 	items := publicListings(rowsToDTO(rows))
+	if err := r.applyShelfMarkup(ctx, query.DistributionSiteCode, items); err != nil {
+		return nil, err
+	}
 	baseQuery := query
 	baseQuery.Zone = ""
 	items = filterPublicListings(items, baseQuery)
@@ -228,15 +231,63 @@ func copyPublicZoneCounts(counts map[string]int64) map[string]int64 {
 	return copied
 }
 
-func (r *Repository) FindPublic(ctx context.Context, id uint64) (*ListingDTO, error) {
+func (r *Repository) FindPublic(ctx context.Context, id uint64, siteCode string) (*ListingDTO, error) {
 	dto, err := r.findDTO(ctx, "l.id = ? AND l.status = ? AND l.review_status = ? AND l.in_transaction = ?", id, "published", "approved", false)
 	if err != nil {
 		return nil, err
 	}
 	applyPublicListingURLs(dto)
+	markups, err := r.shelfMarkupByListingID(ctx, siteCode, []uint64{dto.ID})
+	if err != nil {
+		return nil, err
+	}
+	dto.PriceCent += markups[dto.ID]
 	return dto, nil
 }
 
+func (r *Repository) applyShelfMarkup(ctx context.Context, siteCode string, items []ListingDTO) error {
+	if siteCode == "" || len(items) == 0 {
+		return nil
+	}
+	ids := make([]uint64, 0, len(items))
+	for _, item := range items {
+		ids = append(ids, item.ID)
+	}
+	markups, err := r.shelfMarkupByListingID(ctx, siteCode, ids)
+	if err != nil {
+		return err
+	}
+	for i := range items {
+		items[i].PriceCent += markups[items[i].ID]
+	}
+	return nil
+}
+
+func (r *Repository) shelfMarkupByListingID(ctx context.Context, siteCode string, listingIDs []uint64) (map[uint64]int64, error) {
+	result := make(map[uint64]int64, len(listingIDs))
+	if siteCode == "" || len(listingIDs) == 0 {
+		return result, nil
+	}
+	type markupRow struct {
+		ListingID        uint64 `gorm:"column:listing_id"`
+		MarkupAmountCent int64  `gorm:"column:markup_amount_cent"`
+	}
+	var rows []markupRow
+	if err := r.db.WithContext(ctx).Table("distribution_site_accounts AS dsa").
+		Select("dsa.listing_id, COALESCE(dsa.markup_amount_cent, 0) AS markup_amount_cent").
+		Joins("INNER JOIN distribution_sites AS ds ON ds.id = dsa.site_id AND ds.site_code = ? AND ds.status = 'active'", siteCode).
+		Where("dsa.display_status = 'enabled' AND dsa.listing_id IN ?", listingIDs).
+		Scan(&rows).Error; err != nil {
+		return nil, err
+	}
+	for _, row := range rows {
+		if row.MarkupAmountCent > 0 {
+			result[row.ListingID] = row.MarkupAmountCent
+		}
+	}
+	return result, nil
+}
+
 func (r *Repository) FindPublicCoverKey(ctx context.Context, id uint64) (string, error) {
 	return r.FindPublicScreenshotKey(ctx, id, 0)
 }