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/service_test.go

@@ -348,8 +348,6 @@ func TestApplyPublicListingURLsHidesSourceChannel(t *testing.T) {
 	}
 }
 
-
-
 func uint64Pointer(value uint64) *uint64 {
 	return &value
 }
@@ -703,7 +701,7 @@ func TestListPublicWithDistributionSiteCode(t *testing.T) {
 	site := model.DistributionSite{SiteCode: "site_alpha", SiteName: "分销A", Domain: "a.com", Status: "active", DisplayAccountEnabled: true}
 	db.Create(&site)
 
-	dsa := model.DistributionSiteAccount{SiteID: site.ID, AccountID: account1.ID, ListingID: l1.ID, DisplayStatus: "enabled"}
+	dsa := model.DistributionSiteAccount{SiteID: site.ID, AccountID: account1.ID, ListingID: l1.ID, DisplayStatus: "enabled", MarkupAmountCent: 10000}
 	db.Create(&dsa)
 
 	res, err := repo.ListPublic(context.Background(), PublicListQuery{
@@ -715,6 +713,24 @@ func TestListPublicWithDistributionSiteCode(t *testing.T) {
 	if len(res.Items) != 1 || res.Items[0].ListingNo != "L101" {
 		t.Fatalf("expected only L101, got %+v", res.Items)
 	}
+	if res.Items[0].PriceCent != 11000 {
+		t.Fatalf("expected public price 11000 with markup, got %d", res.Items[0].PriceCent)
+	}
+
+	detail, err := repo.FindPublic(context.Background(), l1.ID, "site_alpha")
+	if err != nil {
+		t.Fatalf("FindPublic err: %v", err)
+	}
+	if detail.PriceCent != 11000 {
+		t.Fatalf("expected detail price 11000 with markup, got %d", detail.PriceCent)
+	}
+	mainDetail, err := repo.FindPublic(context.Background(), l1.ID, "")
+	if err != nil {
+		t.Fatalf("FindPublic main err: %v", err)
+	}
+	if mainDetail.PriceCent != 1000 {
+		t.Fatalf("main site must keep original price, got %d", mainDetail.PriceCent)
+	}
 
 	allRes, err := repo.ListPublic(context.Background(), PublicListQuery{})
 	if err != nil {
@@ -946,5 +962,3 @@ func TestListMineSiteIsolation(t *testing.T) {
 		t.Fatalf("expected 2 listings, got %d", len(allItems))
 	}
 }
-
-