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.Protobuf/CMSMicroservice.Protobuf.csproj

@@ -3,7 +3,7 @@
     <TargetFramework>net9.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
     <Nullable>enable</Nullable>
-    <Version>0.0.195</Version>
+    <Version>0.0.196</Version>
     <DebugType>None</DebugType>
     <DebugSymbols>False</DebugSymbols>
     <GeneratePackageOnBuild>False</GeneratePackageOnBuild>

src/CMSMicroservice.Protobuf/Protos/discountproduct.proto

@@ -163,6 +163,7 @@ message GetDiscountProductsRequest
     google.protobuf.BoolValue in_stock = 6;
     int32 page_number = 7;
     int32 page_size = 8;
+    google.protobuf.StringValue sort_by = 9;
 }
 
 message GetDiscountProductsResponse
@@ -184,6 +185,7 @@ message DiscountProductDto
     int32 view_count = 9;
     bool is_active = 10;
     google.protobuf.Timestamp created = 11;
+    int32 sale_count = 12;
 }
 
 // ===== Product Image Gallery Messages =====