补全分销分账结算闭环并修复站点越权

- 权限落库：新增 000066 迁移，注册 11 个 distribution:* 权限并授权 super_admin/ops/finance
- 越权修复：siteAccessAllowed 校验贯穿站点/规则/订单/展示/支付通道/结算全部按 ID 操作
- 分账闭环：SplitSettlement 按比例拆分分成基数，销售加价归卖出方，尾差记入 rounding_adjustment_cent 归平台；支付快照与退款重算均按拆分写入参与方金额
- 结算批次：创建时聚合周期内待结算订单生成明细并汇总金额，结算时校验明细与总额一致后联动置位财务快照
- 手工补数接口禁止覆盖已有快照并写入审计日志
- 杂项：二维码池校验站点启用状态且不吞真实 DB 错误；绑定支付通道校验商户配置存在；表探测改为 sync.Once 缓存

backend/internal/modules/chat/listing_group.go

@@ -306,11 +306,18 @@ func fetchUnusedQrCode(tx *gorm.DB) (*model.ChatQrCode, error) {
 
 func fetchUnusedQrCodeForListing(tx *gorm.DB, listingID uint64) (*model.ChatQrCode, error) {
 	var relation model.DistributionSiteAccount
-	if err := tx.Where("listing_id = ? AND display_status = 'enabled'", listingID).Order("id ASC").First(&relation).Error; err == nil {
+	// 仅匹配启用中的分销站点，真实 DB 错误直接返回，避免误回退到全局二维码池。
+	err := tx.Table("distribution_site_accounts AS relation").
+		Select("relation.*").
+		Joins("JOIN distribution_sites AS site ON site.id = relation.site_id AND site.status = 'active'").
+		Where("relation.listing_id = ? AND relation.display_status = 'enabled'", listingID).
+		Order("relation.id ASC").
+		Scan(&relation).Error
+	if err != nil {
+		return nil, err
+	}
+	if relation.ID != 0 {
 		return fetchUnusedQrCodeForSite(tx, &relation.SiteID)
-	} else if !errors.Is(err, gorm.ErrRecordNotFound) {
-		// 兼容尚未执行分销迁移的环境，继续使用全局二维码池。
-		return fetchUnusedQrCodeForSite(tx, nil)
 	}
 	return fetchUnusedQrCodeForSite(tx, nil)
 }

backend/internal/modules/chat/qrcode_test.go

@@ -23,6 +23,8 @@ func setupQrCodeTestDB(t *testing.T) *gorm.DB {
 	}
 	if err := db.AutoMigrate(
 		&model.ChatQrCode{},
+		&model.DistributionSite{},
+		&model.DistributionSiteAccount{},
 		&model.ChatConversation{},
 		&model.ChatParticipant{},
 		&model.ChatMessage{},