Refactor EnvelopeTypeController to use MediatR

Replace IEnvelopeTypeService with IMediator in EnvelopeTypeController and update GetAllAsync to use ReadEnvelopeTypesQuery. Remove obsolete service-based code and attributes. Also, remove AsNoTracking() from repository query in ReadEnvelopeTypesQueryHandler.

EnvelopeGenerator.Application/EnvelopeTypes/Queries/ReadEnvelopeTypesQuery.cs

@@ -39,7 +39,7 @@ public class ReadEnvelopeTypesQueryHandler : IRequestHandler<ReadEnvelopeTypesQu
     /// <returns></returns>
     public async Task<IEnumerable<EnvelopeTypeDto>> Handle(ReadEnvelopeTypesQuery request, CancellationToken cancellationToken)
     {
-        var types = await _repository.Query.AsNoTracking().ToListAsync(cancellationToken);
+        var types = await _repository.Query.ToListAsync(cancellationToken);
         return _mapper.Map<IEnumerable<EnvelopeTypeDto>>(types);
     }
 }