feat: 给 PackageUsage 添加 package_name 快照字段，修复企业卡列表 carrier_name/package_name 为空问题

- 迁移 000099：tb_package_usage 新增 package_name 列，回填历史数据
- PackageUsage model 添加 PackageName 字段（与 DataResetCycle 保持一致的快照设计）
- 4 处 PackageUsage 创建点补充 PackageName 快照（order/service.go + auto_purchase.go）
- EnterpriseCard ListCards：carrier_name 直接取 card.CarrierName，package_name 通过
  DISTINCT ON 批量查当前生效主套餐，单次查询覆盖整页，无 N+1

internal/task/auto_purchase.go

@@ -440,6 +440,7 @@ func (h *AutoPurchaseHandler) activateMainPackage(
 		},
 		OrderID:                   order.ID,
 		PackageID:                 pkg.ID,
+		PackageName:               pkg.PackageName,
 		UsageType:                 order.OrderType,
 		DataLimitMB:               pkg.RealDataMB,
 		Status:                    status,
@@ -510,6 +511,7 @@ func (h *AutoPurchaseHandler) activateAddonPackage(
 		},
 		OrderID:        order.ID,
 		PackageID:      pkg.ID,
+		PackageName:    pkg.PackageName,
 		UsageType:      order.OrderType,
 		DataLimitMB:    pkg.RealDataMB,
 		Status:         constants.PackageUsageStatusActive,