feat: extend discount product gRPC API with sort_by and sale_count

- Add sort_by (StringValue) to GetDiscountProductsRequest proto to enable dynamic sorting
- Add sale_count (int32) to DiscountProductDto proto for top-seller exposure
- Update GetDiscountProductsQuery with SortBy property
- Update GetDiscountProductsQueryHandler to use ApplyOrder(SortBy) with fallback to Created desc; project SaleCount in SELECT
- Add SortBy and SaleCount Mapster mappings in DiscountProductProfile
- Bump CMSMicroservice.Protobuf version to 0.0.196

Co-authored-by: Cursor <cursoragent@cursor.com>

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

@@ -11,6 +11,7 @@ public class GetDiscountProductsQuery : IRequest<GetDiscountProductsResponseDto>
     public bool? IsActive { get; set; }
     public int? MinPrice { get; set; }
     public int? MaxPrice { get; set; }
+    public string? SortBy { get; set; }
 }
 
 public class GetDiscountProductsResponseDto

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

@@ -1,3 +1,4 @@
+using CMSMicroservice.Application.Common.Extensions;
 using CMSMicroservice.Application.Common.Interfaces;
 using CMSMicroservice.Application.Common.Models;
 using MediatR;
@@ -51,13 +52,16 @@ 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);
+
         var totalCount = await query.CountAsync(cancellationToken);
 
-        // Apply pagination
         var pagination = request.PaginationQuery ?? new PaginationState { PageNumber = 1, PageSize = 10 };
-        
+
         var products = await query
-            .OrderByDescending(p => p.Created)
             .Skip((pagination.PageNumber - 1) * pagination.PageSize)
             .Take(pagination.PageSize)
             .Select(p => new DiscountProductDto