feat(distribution): 补齐退款加价回退、本站自卖与开通默认规则

退款时压缩卖方加价，人工/自动批次仅完结单可入账，号主收入进主站钱包；仲裁后重算释放并支持作废未入账 DS。开通时四种模式按默认生效，对外口径合并为 35/40/25，不再单独展示通道费。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/internal/modules/distribution/lifecycle_test.go

@@ -472,3 +472,59 @@ func TestApplyRefundTxWithCheckoutAndDeposit(t *testing.T) {
 		t.Fatalf("distributorParty.IncomeAmountCent = %d, want 2513", distributorParty.IncomeAmountCent)
 	}
 }
+
+func TestApplyRefundTxClampsSellerMarkup(t *testing.T) {
+	db := distributionTestDB(t)
+	now := time.Now()
+	site := model.DistributionSite{SiteCode: "markup_refund", SiteName: "加价回退站", Domain: "markup-refund.dist.com", Status: "active"}
+	if err := db.Create(&site).Error; err != nil {
+		t.Fatal(err)
+	}
+	rule := model.DistributionRuleVersion{
+		SiteID: &site.ID, Mode: ModeTwoPartyPlatformReceive, Version: 1, Status: "active",
+		PlatformReceiveRatio: 35, DistributorSellRatio: 40,
+		ServiceFeeValue: 25, ServiceFeeUnit: ServiceFeeUnitPercent, PaymentFeeBPS: 50,
+		EffectiveFrom: now.Add(-time.Hour),
+	}
+	if err := db.Create(&rule).Error; err != nil {
+		t.Fatal(err)
+	}
+	order := model.RentalOrder{
+		OrderNo: "ORD-MARKUP-REFUND", ListingID: 1, AccountID: 2, OwnerID: 3, RenterID: 4, Status: "completed",
+		RentAmountCent: 10000, OwnerRentAmountCent: 6000, ShelfMarkupCent: 3000,
+		DistributionSiteID: &site.ID, DistributionRuleVersionID: &rule.ID, DistributionMode: ModeTwoPartyPlatformReceive,
+	}
+	if err := db.Create(&order).Error; err != nil {
+		t.Fatal(err)
+	}
+	if err := SnapshotPaidOrderTx(db, order.ID, 10000); err != nil {
+		t.Fatal(err)
+	}
+	var seller model.DistributionOrderParty
+	if err := db.Where("order_id = ? AND party_role = ?", order.ID, "distributor_sell").First(&seller).Error; err != nil {
+		t.Fatal(err)
+	}
+	if seller.IncomeAmountCent != 3400 {
+		t.Fatalf("paid seller = %d, want 400+3000", seller.IncomeAmountCent)
+	}
+
+	if err := ApplyRefundTx(db, order.ID, 2000); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.Where("order_id = ? AND party_role = ?", order.ID, "distributor_sell").First(&seller).Error; err != nil {
+		t.Fatal(err)
+	}
+	if seller.IncomeAmountCent != 2000 {
+		t.Fatalf("partial refund seller markup = %d, want 2000", seller.IncomeAmountCent)
+	}
+
+	if err := ApplyRefundTx(db, order.ID, 10000); err != nil {
+		t.Fatal(err)
+	}
+	if err := db.Where("order_id = ? AND party_role = ?", order.ID, "distributor_sell").First(&seller).Error; err != nil {
+		t.Fatal(err)
+	}
+	if seller.IncomeAmountCent != 0 {
+		t.Fatalf("full refund must return seller markup, got %d", seller.IncomeAmountCent)
+	}
+}