Add recent receiver suggestions query and DTO

Introduce `RecentReceiverSuggestionDto` to represent recent receiver suggestions with `FullName` and `EmailAddress`.

Add `ReadRecentReceiverSuggestionsQuery` to retrieve recent receiver suggestions scoped by sender username and limited to 3-5 results.

Implement `ReadRecentReceiverSuggestionsQueryHandler` to process the query using Entity Framework Core and AutoMapper.

Update `MappingProfile` to map `EnvelopeReceiver` to `RecentReceiverSuggestionDto`.

EnvelopeGenerator.Application/EnvelopeReceivers/MappingProfile.cs

@@ -16,5 +16,9 @@ public class MappingProfile : Profile
     public MappingProfile()
     {
         CreateMap<Receiver, ReceiverDto>();
+
+        CreateMap<EnvelopeReceiver, RecentReceiverSuggestionDto>()
+            .ForMember(dest => dest.FullName, opt => opt.MapFrom(src => src.Name))
+            .ForMember(dest => dest.EmailAddress, opt => opt.MapFrom(src => src.Receiver.EmailAddress));
     }
 }