Standardize DTO naming and namespaces for MassData

Refactored DTO class and namespace names from Massdata* to MassData* in DbFirst.Contracts. Updated all relevant application files to use the correct DTO namespaces for Catalogs and MassData. Adjusted _Imports.razor to include new DTO namespaces and removed unused usings. These changes improve code consistency and reduce namespace-related errors.

DbFirst.Contracts/Massdata/MassdataWriteDto.cs

@@ -4,9 +4,9 @@ using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
 
-namespace DbFirst.Contracts.Massdata
+namespace DbFirst.Contracts.MassData
 {
-    internal class MassdataWriteDto
+    internal class MassDataWriteDto
     {
     }
 }