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/Common/Dto/Receiver/RecentReceiverSuggestionDto.cs

@@ -0,0 +1,8 @@
+namespace EnvelopeGenerator.Application.Common.Dto.Receiver;
+
+public class RecentReceiverSuggestionDto
+{
+    public required string FullName { get; set; }
+
+    public required string EmailAddress { get; set; }
+}