feat(service): add ReadLastUsedReceiverNameByMail method to IEnvelopeReceiverService and EnvelopeReceiverService

- Added `ReadLastUsedReceiverNameByMail` method to `IEnvelopeReceiverService` interface.
- Implemented `ReadLastUsedReceiverNameByMail` method in `EnvelopeReceiverService` to retrieve the last used receiver's name by email and handle results with `DataResult`.

EnvelopeGenerator.Application/Contracts/IEnvelopeReceiverService.cs

@@ -25,5 +25,7 @@ namespace EnvelopeGenerator.Application.Contracts
         Task<DataResult<bool>> IsExisting(string envelopeReceiverId);
 
         Task<DataResult<IEnumerable<EnvelopeReceiverDto>>> ReadByUsernameAsync(string username, int? min_status = null, int? max_status = null, params int[] ignore_statuses);
+
+        Task<DataResult<string?>> ReadLastUsedReceiverNameByMail(string mail);
     }
 }