feat(sorting): implement ApplyOrderWithInStockPriority method for enhanced product sorting

- Added ApplyOrderWithInStockPriority method to prioritize in-stock products in queries.
- Updated GetDiscountProductsQueryHandler and GetCustomerProductsByFilterQueryHandler to utilize the new sorting method, ensuring in-stock items are listed first followed by user-defined sorting or creation date.
- Improved overall query handling for product availability and sorting logic.

src/CMSMicroservice.Application/DiscountShopCQ/Queries/GetDiscountProducts/GetDiscountProductsQueryHandler.cs

@@ -57,10 +57,8 @@ public class GetDiscountProductsQueryHandler : IRequestHandler<GetDiscountProduc
             query = query.Where(p => p.Price <= request.MaxPrice.Value);
         }
 
-        if (!string.IsNullOrEmpty(request.SortBy))
-            query = query.ApplyOrder(request.SortBy);
-        else
-            query = query.OrderByDescending(p => p.Created);
+        // موجودی‌دارها اول، سپس سورت درخواستی
+        query = query.ApplyOrderWithInStockPriority(request.SortBy, p => p.RemainingCount > 0);
 
         var totalCount = await query.CountAsync(cancellationToken);