fix(distribution): 结算幂等与退款口径加固，补关单释放与回归测试

- 结算明细加唯一键 (order_id, party_id)：自动释放与手工批次并发时以唯一键冲突为准跳过该参与方，不再重复入账
- 自动释放先无锁筛出本站未入账参与方，收敛加锁范围；手工批次建批次后先锁周期内财务快照，与自动释放串行化
- 累计退款额改为「本次回调金额与已退款成功流水合计取较大值」，多笔退款与退款结果重复回调不再把口径写小
- 关单三路径（AdminClose / AdminRejectRefund 的 close 分支 / AdminSeal）补写 release_at，接线原死代码 EnsureCompletedReleaseAtTx
- 仲裁分销重算改用实际退款额（扣除押金暂扣），避免站点被多扣
- 订单列表与详情的提价分成取 min(收入, 货架加价)，退款压缩加价后不再显示负数
- 新增迁移 000070（结算明细唯一键）、000071（补回填 closed 订单释放时间）
- 新增 5 个测试文件：结算幂等与展示钳制、结算 job 幂等、累计退款、关单补写释放时间、仲裁押金暂扣口径

backend/internal/modules/payment/refund.go

@@ -421,11 +421,22 @@ func (r *Repository) updateOrderRefundStatus(ctx context.Context, orderID uint64
 		if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).First(&order, orderID).Error; err != nil {
 			return err
 		}
+		// 同一订单可能多笔退款，且退款结果查询会重复回调：
+		// 以已退款成功流水合计为口径，并取本次金额与累计额的较大值，
+		// 保证 order.RefundAmountCent 单调不回退、重复回调幂等。
+		var refundedTotal int64
+		if err := tx.Model(&model.PaymentOrder{}).
+			Where("order_id = ? AND status = ?", orderID, "refunded").
+			Where("biz_type IN ?", refundBizTypes).
+			Select("COALESCE(SUM(amount_cent), 0)").Scan(&refundedTotal).Error; err != nil {
+			return err
+		}
+		cumulative := max(refundAmountCent, refundedTotal)
 		now := time.Now()
 		order.RefundStatus = "refunded"
-		order.RefundAmountCent = refundAmountCent
+		order.RefundAmountCent = cumulative
 		order.RefundedAt = &now
-		if bizType == "admin_refund" && order.Status == "completed" && refundAmountCent >= order.RentAmountCent+order.DepositAmountCent {
+		if bizType == "admin_refund" && order.Status == "completed" && cumulative >= order.RentAmountCent+order.DepositAmountCent {
 			if err := rentergrowth.RevokeOrderCompleted(tx, &order); err != nil {
 				return err
 			}
@@ -433,7 +444,7 @@ func (r *Repository) updateOrderRefundStatus(ctx context.Context, orderID uint64
 		if err := tx.Save(&order).Error; err != nil {
 			return err
 		}
-		return distribution.ApplyRefundTx(tx, orderID, refundAmountCent)
+		return distribution.ApplyRefundTx(tx, orderID, cumulative)
 	})
 }
 func (r *Repository) markOrderRefunding(ctx context.Context, orderID uint64, refundAmountCent int64) error {