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/service_test.go

@@ -891,6 +891,14 @@ func TestCreateListingWithDistributionSiteCode(t *testing.T) {
 		t.Fatalf("expected enabled, got %s", dsa.DisplayStatus)
 	}
 
+	var stored model.RentalListing
+	if err := db.First(&stored, dto.ID).Error; err != nil {
+		t.Fatalf("load listing: %v", err)
+	}
+	if stored.SourceChannel != site.SiteCode {
+		t.Fatalf("stored source_channel = %q, want %q", stored.SourceChannel, site.SiteCode)
+	}
+
 	// 验证审核工作台列表展示分销站来源
 	pending, err := repo.ListPendingReview(context.Background())
 	if err != nil {
@@ -904,6 +912,43 @@ func TestCreateListingWithDistributionSiteCode(t *testing.T) {
 	}
 }
 
+func TestCreateListingInvalidDistributionSiteCode(t *testing.T) {
+	db := database.NewTestDB()
+	if err := database.MigrateListingLifecycleTestSchema(db); err != nil {
+		t.Fatalf("migrate err: %v", err)
+	}
+	repo := NewRepository(db, nil)
+
+	user := model.User{Phone: "18800000011", Nickname: "分销卖家", RealnameStatus: "verified", Status: "active"}
+	db.Create(&user)
+
+	inactive := model.DistributionSite{
+		SiteCode:              "dist_inactive",
+		SiteName:              "已停用分销站",
+		Domain:                "inactive.example.com",
+		Status:                "disabled",
+		DisplayAccountEnabled: true,
+	}
+	db.Create(&inactive)
+
+	req := CreateRequest{Title: "无效站点商品", ServerRegion: "QQ", LoginPlatform: "PC", PriceCent: 1000}
+
+	if _, err := repo.Create(context.Background(), user.ID, req, true, 0, "does_not_exist"); !errors.Is(err, ErrDistributionSiteInvalid) {
+		t.Fatalf("unknown site err = %v, want ErrDistributionSiteInvalid", err)
+	}
+	if _, err := repo.Create(context.Background(), user.ID, req, true, 0, "dist_inactive"); !errors.Is(err, ErrDistributionSiteInvalid) {
+		t.Fatalf("inactive site err = %v, want ErrDistributionSiteInvalid", err)
+	}
+
+	var count int64
+	if err := db.Model(&model.RentalListing{}).Count(&count).Error; err != nil {
+		t.Fatal(err)
+	}
+	if count != 0 {
+		t.Fatalf("invalid site must not create listing, got %d", count)
+	}
+}
+
 func TestListMineSiteIsolation(t *testing.T) {
 	db := database.NewTestDB()
 	if err := database.MigrateListingLifecycleTestSchema(db); err != nil {