refactor: 出库时间更名为首次购买套餐时间，换货新资产不再按换货完成时间记录

- 字段 outbound_at → first_purchase_at，记录表 tb_asset_outbound_record → tb_asset_first_purchase_record，接口 /outbound-records → /first-purchase-records，筛选参数与导出列同步更名
- 换货后的新资产不因换货写入，在当前世代真正支付套餐订单时才记录；记录来源只保留 order / backfill，去掉换货单字段
- 迁移 000266 重命名列、表、索引与约束；同步 Spec、设计、任务与前端接口变更说明

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/query/packagesilence/query.go

@@ -1,4 +1,4 @@
-// Package packagesilence 提供沉默期延期订单、批次、即将过期 / 已过期套餐与出库记录的只读查询。
+// Package packagesilence 提供沉默期延期订单、批次、即将过期 / 已过期套餐与首次购买套餐记录的只读查询。
 package packagesilence
 
 import (
@@ -308,13 +308,13 @@ func (q *Query) FetchUsages(ctx context.Context, query *gorm.DB, offset, limit i
 	return items, nil
 }
 
-// ListOutboundRecords 按资产查询各世代出库记录（叠加资产数据范围）。
-func (q *Query) ListOutboundRecords(ctx context.Context, assetType string, assetID uint) ([]dto.AssetOutboundRecordResponse, error) {
+// ListFirstPurchaseRecords 按资产查询各世代首次购买套餐记录（叠加资产数据范围）。
+func (q *Query) ListFirstPurchaseRecords(ctx context.Context, assetType string, assetID uint) ([]dto.AssetFirstPurchaseRecordResponse, error) {
 	if assetType == "card" {
-		assetType = constants.OutboundAssetTypeIotCard
+		assetType = constants.FirstPurchaseAssetTypeIotCard
 	}
 	table := "tb_iot_card"
-	if assetType == constants.OutboundAssetTypeDevice {
+	if assetType == constants.FirstPurchaseAssetTypeDevice {
 		table = "tb_device"
 	}
 	var count int64
@@ -324,28 +324,26 @@ func (q *Query) ListOutboundRecords(ctx context.Context, assetType string, asset
 	if count == 0 {
 		return nil, errors.New(errors.CodeForbidden, "无权限操作该资源或资源不存在")
 	}
-	var records []model.AssetOutboundRecord
+	var records []model.AssetFirstPurchaseRecord
 	if err := q.db.WithContext(ctx).Where("asset_type = ? AND asset_id = ?", assetType, assetID).Order("generation DESC").Find(&records).Error; err != nil {
-		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询出库记录失败")
+		return nil, errors.Wrap(errors.CodeDatabaseError, err, "查询首次购买套餐记录失败")
 	}
-	items := make([]dto.AssetOutboundRecordResponse, 0, len(records))
+	items := make([]dto.AssetFirstPurchaseRecordResponse, 0, len(records))
 	for _, record := range records {
-		items = append(items, dto.AssetOutboundRecordResponse{
+		items = append(items, dto.AssetFirstPurchaseRecordResponse{
 			ID: record.ID, AssetType: record.AssetType, AssetID: record.AssetID, AssetIdentifier: record.AssetIdentifierSnapshot,
-			Generation: record.Generation, OutboundAt: record.OutboundAt, Source: record.Source, SourceName: outboundSourceName(record.Source),
-			OrderNo: record.OrderNo, ExchangeNo: record.ExchangeNo, EndedAt: record.EndedAt, EndReason: record.EndReason, CreatedAt: record.CreatedAt,
+			Generation: record.Generation, FirstPurchaseAt: record.FirstPurchaseAt, Source: record.Source, SourceName: firstPurchaseSourceName(record.Source),
+			OrderNo: record.OrderNo, EndedAt: record.EndedAt, EndReason: record.EndReason, CreatedAt: record.CreatedAt,
 		})
 	}
 	return items, nil
 }
 
-func outboundSourceName(source string) string {
+func firstPurchaseSourceName(source string) string {
 	switch source {
-	case constants.OutboundSourceOrder:
+	case constants.FirstPurchaseSourceOrder:
 		return "首次购买套餐"
-	case constants.OutboundSourceExchange:
-		return "换货新资产"
-	case constants.OutboundSourceBackfill:
+	case constants.FirstPurchaseSourceBackfill:
 		return "历史回填"
 	default:
 		return source