Revert "refactor: 清理租户API旧模块代码"

This reverts commit 992930a821.

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

@@ -0,0 +1,15 @@
+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; }
+}