refactor: 清理租户API旧模块代码

src/Application/TakeoutSaaS.Application/App/Billings/Queries/GetBillingDetailQuery.cs

@@ -1,15 +0,0 @@
-using MediatR;
-using TakeoutSaaS.Application.App.Billings.Dto;
-
-namespace TakeoutSaaS.Application.App.Billings.Queries;
-
-/// <summary>
-/// 查询账单详情（含明细项）。
-/// </summary>
-public sealed record GetBillingDetailQuery : IRequest<BillingDetailDto>
-{
-    /// <summary>
-    /// 账单 ID（雪花算法）。
-    /// </summary>
-    public long BillingId { get; init; }
-}