fix(invitation): 返利归因统一为「订单所属站点」，买卖两端一致

- 买家端不再强制记主站（原 buyerSiteID=0），卖家端不再记拆分方站点，两端统一取 orderSiteID
- orderSiteID = 订单所属站点（>0 时）；订单未记站点但存在分销拆分时回退到拆分方站点，避免主站替分站订单买单
- 该站点同时用于取返利配置(GetRebateConfig)、返利流水与钱包流水的 distribution_site_id，分站后台由此能看到本站返利支出
- 基数口径未改动，非分销订单行为与改前一致；历史 9 笔数据不订正，规则自此生效
- 测试：更新跨站用例断言；新增订单站点归因用例（校验站点专属比例 0.5 与钱包流水站点维度）

backend/internal/modules/invitation/repository.go

@@ -386,27 +386,30 @@ func (r *Repository) ProcessOrderInvitationRebate(ctx context.Context, tx *gorm.
 
 	now := time.Now()
 
+	// 返利归因站点（统一规则）：成本一律由「订单所属站点」承担，并使用该站点自己的返利配置。
+	// 订单未记录站点但存在分销拆分时，回退到拆分方站点（钱实际归它），
+	// 避免再次出现「主站替分站订单买单」的倒贴。
+	orderSiteID := distributorSiteID
+	if order.DistributionSiteID != nil && *order.DistributionSiteID > 0 {
+		orderSiteID = *order.DistributionSiteID
+	}
+
 	// 1. 买家端处理（租客 RenterID）
 	var buyerInvitation model.UserInvitation
 	if err := tx.Where("invitee_id = ? AND status = ?", order.RenterID, StatusActive).First(&buyerInvitation).Error; err == nil {
 		if buyerInvitation.VerifiedAt != nil {
 			var inviter model.User
 			if err := tx.First(&inviter, buyerInvitation.InviterID).Error; err == nil && inviter.RealnameStatus == "verified" && inviter.ID != order.RenterID {
-				// 买家端基数：若有分销售卖拆分按 platformSellCent，否则按整单毛利对半拆
+				// 买家端基数：有分销售卖拆分按 platformSellCent，否则按整单毛利对半拆；归因站点统一取 orderSiteID
 				var buyerBasisCent int64
-				var buyerSiteID uint64
 				if platformSellCent > 0 {
 					buyerBasisCent = int64(math.Floor(float64(platformSellCent) / 2.0))
-					buyerSiteID = 0
 				} else {
 					buyerBasisCent = int64(math.Floor(float64(orderGrossProfitCent) / 2.0))
-					if order.DistributionSiteID != nil {
-						buyerSiteID = *order.DistributionSiteID
-					}
 				}
 
 				if buyerBasisCent > 0 {
-					cfg, _ := r.GetRebateConfig(ctx, buyerSiteID)
+					cfg, _ := r.GetRebateConfig(ctx, orderSiteID)
 					if cfg == nil || cfg.Enabled {
 						rate, cycle, days := CalculateRebateRate(*buyerInvitation.VerifiedAt, now, cfg)
 						rebateCent := int64(math.Round(float64(buyerBasisCent) * rate))
@@ -415,7 +418,7 @@ func (r *Repository) ProcessOrderInvitationRebate(ctx context.Context, tx *gorm.
 							ledger := model.InvitationRebateLedger{
 								OrderID:              order.ID,
 								OrderNo:              order.OrderNo,
-								DistributionSiteID:   buyerSiteID,
+								DistributionSiteID:   orderSiteID,
 								InviterID:            buyerInvitation.InviterID,
 								InviteeID:            order.RenterID,
 								TradeRole:            "buyer",
@@ -432,7 +435,7 @@ func (r *Repository) ProcessOrderInvitationRebate(ctx context.Context, tx *gorm.
 							if err := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&ledger).Error; err == nil && ledger.ID > 0 {
 								_ = wallet.AppendEntries(tx, wallet.Entry{
 									UserID:             buyerInvitation.InviterID,
-									DistributionSiteID: buyerSiteID,
+									DistributionSiteID: orderSiteID,
 									Direction:          "in",
 									AmountCent:         rebateCent,
 									BalanceType:        "available",
@@ -454,21 +457,16 @@ func (r *Repository) ProcessOrderInvitationRebate(ctx context.Context, tx *gorm.
 		if sellerInvitation.VerifiedAt != nil {
 			var inviter model.User
 			if err := tx.First(&inviter, sellerInvitation.InviterID).Error; err == nil && inviter.RealnameStatus == "verified" && inviter.ID != order.OwnerID {
-				// 卖家端基数：若有分站收号拆分按 distributorReceiveCent（从分站出），否则按整单毛利对半拆
+				// 卖家端基数：有分站收号拆分按 distributorReceiveCent，否则按整单毛利对半拆；归因站点统一取 orderSiteID
 				var sellerBasisCent int64
-				var sellerSiteID uint64
 				if distributorReceiveCent > 0 {
 					sellerBasisCent = int64(math.Floor(float64(distributorReceiveCent) / 2.0))
-					sellerSiteID = distributorSiteID
 				} else {
 					sellerBasisCent = int64(math.Floor(float64(orderGrossProfitCent) / 2.0))
-					if order.DistributionSiteID != nil {
-						sellerSiteID = *order.DistributionSiteID
-					}
 				}
 
 				if sellerBasisCent > 0 {
-					cfg, _ := r.GetRebateConfig(ctx, sellerSiteID)
+					cfg, _ := r.GetRebateConfig(ctx, orderSiteID)
 					if cfg == nil || cfg.Enabled {
 						rate, cycle, days := CalculateRebateRate(*sellerInvitation.VerifiedAt, now, cfg)
 						rebateCent := int64(math.Round(float64(sellerBasisCent) * rate))
@@ -477,7 +475,7 @@ func (r *Repository) ProcessOrderInvitationRebate(ctx context.Context, tx *gorm.
 							ledger := model.InvitationRebateLedger{
 								OrderID:              order.ID,
 								OrderNo:              order.OrderNo,
-								DistributionSiteID:   sellerSiteID,
+								DistributionSiteID:   orderSiteID,
 								InviterID:            sellerInvitation.InviterID,
 								InviteeID:            order.OwnerID,
 								TradeRole:            "seller",
@@ -494,7 +492,7 @@ func (r *Repository) ProcessOrderInvitationRebate(ctx context.Context, tx *gorm.
 							if err := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&ledger).Error; err == nil && ledger.ID > 0 {
 								_ = wallet.AppendEntries(tx, wallet.Entry{
 									UserID:             sellerInvitation.InviterID,
-									DistributionSiteID: sellerSiteID,
+									DistributionSiteID: orderSiteID,
 									Direction:          "in",
 									AmountCent:         rebateCent,
 									BalanceType:        "available",

backend/internal/modules/invitation/repository_test.go

@@ -271,16 +271,17 @@ func TestCrossSiteDistributionRebate(t *testing.T) {
 		t.Fatalf("跨站分销返利结算失败: %v", err)
 	}
 
-	// 验证买家端流水：基数 4000 / 2 = 2000，首月 60% = 1200，站点为 0 (主站)
+	// 验证买家端流水：基数 4000 / 2 = 2000，首月 60% = 1200；
+	// 本单未记录归属站点，归因回退到拆分方站点（买卖两端统一，不再记主站）
 	var buyerLedger model.InvitationRebateLedger
 	if err := db.Where("order_id = ? AND trade_role = 'buyer'", order.ID).First(&buyerLedger).Error; err != nil {
 		t.Fatalf("未找到买家端流水: %v", err)
 	}
-	if buyerLedger.DistributionSiteID != 0 || buyerLedger.RebateAmountCent != 1200 {
+	if buyerLedger.DistributionSiteID != distributorSiteID || buyerLedger.RebateAmountCent != 1200 {
 		t.Fatalf("买家端跨站返利错误: siteID=%d, amount=%d", buyerLedger.DistributionSiteID, buyerLedger.RebateAmountCent)
 	}
 
-	// 验证卖家端流水：基数 6000 / 2 = 3000，首月 60% = 1800，站点为 88 (分站)
+	// 验证卖家端流水：基数 6000 / 2 = 3000，首月 60% = 1800，站点同为拆分方站点
 	var sellerLedger model.InvitationRebateLedger
 	if err := db.Where("order_id = ? AND trade_role = 'seller'", order.ID).First(&sellerLedger).Error; err != nil {
 		t.Fatalf("未找到卖家端流水: %v", err)
@@ -290,6 +291,112 @@ func TestCrossSiteDistributionRebate(t *testing.T) {
 	}
 }
 
+// 分销订单的返利归因必须统一到「订单所属站点」并使用该站自己的比例。
+// 修复前买家端被强制记主站（用主站比例），基数却取分站售卖额，导致主站替分站订单倒贴。
+func TestOrderRebateAttrToOrderSiteForDistributionOrder(t *testing.T) {
+	db := setupTestDB(t)
+	repo := NewRepository(db)
+	ctx := context.Background()
+	now := time.Now()
+	verifiedAt := now.AddDate(0, 0, -1).Truncate(time.Second)
+
+	site := model.DistributionSite{
+		SiteCode: "site_attr", SiteName: "归因测试站", Domain: "attr.example.com", Status: "active",
+	}
+	if err := db.Create(&site).Error; err != nil {
+		t.Fatalf("创建站点失败: %v", err)
+	}
+	// 站点专属比例 0.5（主站默认 0.6），用于证明取的是站点配置而非主站配置
+	if err := db.Create(&model.InvitationRebateConfig{
+		DistributionSiteID: site.ID,
+		FirstMonthRate:     0.5,
+		SecondMonthRate:    0.3,
+		SubsequentRate:     0.15,
+		Enabled:            true,
+	}).Error; err != nil {
+		t.Fatalf("创建站点返利配置失败: %v", err)
+	}
+
+	buyerInviter := model.User{Phone: "13800000401", RealnameStatus: "verified", Status: "active"}
+	buyer := model.User{Phone: "13800000402", RealnameStatus: "verified", Status: "active"}
+	sellerInviter := model.User{Phone: "13800000403", RealnameStatus: "verified", Status: "active"}
+	seller := model.User{Phone: "13800000404", RealnameStatus: "verified", Status: "active"}
+	for _, user := range []*model.User{&buyerInviter, &buyer, &sellerInviter, &seller} {
+		if err := db.Create(user).Error; err != nil {
+			t.Fatalf("创建用户失败: %v", err)
+		}
+	}
+	if err := db.Create(&model.UserInvitation{
+		InviterID: buyerInviter.ID, InviteeID: buyer.ID, DistributionSiteID: site.ID,
+		Status: StatusActive, VerifiedAt: &verifiedAt,
+	}).Error; err != nil {
+		t.Fatalf("创建买家邀请关系失败: %v", err)
+	}
+	if err := db.Create(&model.UserInvitation{
+		InviterID: sellerInviter.ID, InviteeID: seller.ID, DistributionSiteID: site.ID,
+		Status: StatusActive, VerifiedAt: &verifiedAt,
+	}).Error; err != nil {
+		t.Fatalf("创建卖家邀请关系失败: %v", err)
+	}
+
+	order := model.RentalOrder{
+		OrderNo:             fmt.Sprintf("ORD-SITE-%d", now.UnixNano()),
+		RenterID:            buyer.ID,
+		OwnerID:             seller.ID,
+		Status:              "completed",
+		SettlementStatus:    "settled",
+		RentAmountCent:      30000,
+		OwnerRentAmountCent: 20000, // 整单毛利 10000
+		DistributionSiteID:  &site.ID,
+	}
+	if err := db.Create(&order).Error; err != nil {
+		t.Fatalf("创建订单失败: %v", err)
+	}
+
+	// 分站自售拆分：distributor_sell 6000（进入 platformSellCent）+ distributor_receive 4000
+	parties := []model.DistributionOrderParty{
+		{OrderID: order.ID, SiteID: site.ID, PartyRole: "distributor_sell", PartyType: "site", PartyID: site.ID, ProfitAmountCent: 6000, IncomeAmountCent: 6000},
+		{OrderID: order.ID, SiteID: site.ID, PartyRole: "distributor_receive", PartyType: "site", PartyID: site.ID, ProfitAmountCent: 4000, IncomeAmountCent: 4000},
+	}
+	if err := db.Create(&parties).Error; err != nil {
+		t.Fatalf("创建分销拆分行失败: %v", err)
+	}
+
+	if err := repo.ProcessOrderInvitationRebate(ctx, db, order.ID); err != nil {
+		t.Fatalf("分销订单返利结算失败: %v", err)
+	}
+
+	// 买家端：基数 6000/2 = 3000，站点比例 0.5 => 1500，归因必须为订单站点
+	var buyerLedger model.InvitationRebateLedger
+	if err := db.Where("order_id = ? AND trade_role = 'buyer'", order.ID).First(&buyerLedger).Error; err != nil {
+		t.Fatalf("未找到买家端流水: %v", err)
+	}
+	if buyerLedger.DistributionSiteID != site.ID || buyerLedger.RateApplied != 0.5 || buyerLedger.RebateAmountCent != 1500 {
+		t.Fatalf("买家端归因/比例错误: site=%d rate=%.2f amount=%d",
+			buyerLedger.DistributionSiteID, buyerLedger.RateApplied, buyerLedger.RebateAmountCent)
+	}
+
+	// 卖家端：基数 4000/2 = 2000，站点比例 0.5 => 1000，归因同为订单站点
+	var sellerLedger model.InvitationRebateLedger
+	if err := db.Where("order_id = ? AND trade_role = 'seller'", order.ID).First(&sellerLedger).Error; err != nil {
+		t.Fatalf("未找到卖家端流水: %v", err)
+	}
+	if sellerLedger.DistributionSiteID != site.ID || sellerLedger.RateApplied != 0.5 || sellerLedger.RebateAmountCent != 1000 {
+		t.Fatalf("卖家端归因/比例错误: site=%d rate=%.2f amount=%d",
+			sellerLedger.DistributionSiteID, sellerLedger.RateApplied, sellerLedger.RebateAmountCent)
+	}
+
+	// 钱包流水同样记在站点维度，分站后台才能看到这笔返利支出
+	var walletLedger model.WalletLedger
+	if err := db.Where("biz_type = ? AND biz_no = ?", "invite_rebate", order.OrderNo).
+		Order("id ASC").First(&walletLedger).Error; err != nil {
+		t.Fatalf("未找到返利钱包流水: %v", err)
+	}
+	if walletLedger.DistributionSiteID != site.ID {
+		t.Fatalf("钱包流水站点维度错误: site=%d, want %d", walletLedger.DistributionSiteID, site.ID)
+	}
+}
+
 // cycleLabel 的比例必须来自实际生效配置，改配置后文案要跟着变，
 // 否则钱包流水备注会与后台比例不一致（历史缺陷）。
 func TestCycleLabelFollowsConfiguredRate(t *testing.T) {