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.WebApi/Common/Mappings/DiscountProductProfile.cs

@@ -23,6 +23,8 @@ public class DiscountProductProfile : IRegister
                 src => src.MinPrice != null ? (int?)src.MinPrice.Value : null)
             .Map(dest => dest.MaxPrice,
                 src => src.MaxPrice != null ? (int?)src.MaxPrice.Value : null)
+            .Map(dest => dest.SortBy,
+                src => string.IsNullOrEmpty(src.SortBy) ? null : src.SortBy)
             .Map(dest => dest.PaginationQuery, src => new PaginationState
             {
                 PageNumber = src.PageNumber > 0 ? src.PageNumber : 1,
@@ -64,6 +66,7 @@ public class DiscountProductProfile : IRegister
                     ThumbnailPath = p.ThumbnailPath ?? string.Empty,
                     RemainingCount = p.RemainingCount,
                     ViewCount = p.ViewCount,
+                    SaleCount = p.SaleCount,
                     IsActive = p.IsActive,
                     Created = Timestamp.FromDateTime(DateTime.UtcNow)
                 });