feat: 添加订单大厅看板 API（四列数据 + 统计 + 重连补偿 + 操作端点）

- 新增 OrderBoardCardDto、OrderBoardResultDto、OrderBoardStatsDto
- 新增看板查询 Query + Handler（board/stats/pending-since）
- IOrderRepository 扩展 GetActiveOrdersAsync、GetOrdersChangedSinceAsync
- EfOrderRepository 实现看板查询方法
- 新增 OrderBoardController（GET board/stats/pending-since + POST accept/reject/complete/confirm）
- 新增 RejectOrderRequest 契约

src/Application/TakeoutSaaS.Application/App/Orders/Handlers/GetOrderBoardStatsQueryHandler.cs

@@ -0,0 +1,39 @@
+using MediatR;
+using TakeoutSaaS.Application.App.Orders.Dto;
+using TakeoutSaaS.Application.App.Orders.Queries;
+using TakeoutSaaS.Domain.Orders.Enums;
+using TakeoutSaaS.Domain.Orders.Repositories;
+
+namespace TakeoutSaaS.Application.App.Orders.Handlers;
+
+/// <summary>
+/// 获取订单看板统计查询处理器。
+/// </summary>
+public sealed class GetOrderBoardStatsQueryHandler(IOrderRepository orderRepository)
+    : IRequestHandler<GetOrderBoardStatsQuery, OrderBoardStatsDto>
+{
+    /// <inheritdoc />
+    public async Task<OrderBoardStatsDto> Handle(GetOrderBoardStatsQuery request, CancellationToken cancellationToken)
+    {
+        // 1. 查询活跃订单
+        var activeOrders = await orderRepository.GetActiveOrdersAsync(
+            request.TenantId, request.StoreId, cancellationToken);
+
+        // 2. 查询今日所有订单
+        var todayStart = DateTime.UtcNow.Date;
+        var todayOrders = await orderRepository.GetOrdersChangedSinceAsync(
+            request.TenantId, request.StoreId, todayStart, cancellationToken);
+
+        // 3. 统计各状态数量
+        var allOrders = activeOrders.Concat(todayOrders).DistinctBy(o => o.Id).ToList();
+
+        return new OrderBoardStatsDto
+        {
+            TodayTotal = allOrders.Count,
+            PendingCount = allOrders.Count(o => o.Status == OrderStatus.AwaitingPreparation),
+            MakingCount = allOrders.Count(o => o.Status == OrderStatus.InProgress),
+            DeliveringCount = allOrders.Count(o => o.Status == OrderStatus.Ready),
+            CompletedCount = allOrders.Count(o => o.Status == OrderStatus.Completed)
+        };
+    }
+}