Refactor ReadEmailQuery to return structured response

Updated ReadEmailQuery to return a new response type,
ReadEmailQueryResponse, which includes both email data
and metadata (e.g., LastSync). Added the Account property
to ReadEmailQuery for specifying the email account.

Refactored ReadEmailQueryHandler to:
- Use IImapEmailService to fetch LastSync metadata.
- Return ReadEmailQueryResponse instead of a collection
  of ReceivedEmailDto.

Introduced ReadEmailQueryResponse class to encapsulate
LastSync and Emails properties.

Updated EmailController to handle the new response
structure, ensuring compatibility with the updated
ReadEmailQuery and its handler.

src/core/DigitalData.MessagingService.Application/EmailReceiving/Queries/ReadEmailQueryResponse.cs

@@ -0,0 +1,17 @@
+#if NET
+using DigitalData.MessagingService.Application.Common.Dto;
+
+namespace DigitalData.MessagingService.Application.EmailReceiving.Queries;
+
+/// <summary>
+/// 
+/// </summary>
+/// <param name="Emails"></param>
+/// <param name="LastSync"></param>
+public class ReadEmailQueryResponse
+{
+    public DateTime? LastSync { get; init; } = null;
+
+    public IEnumerable<ReceivedEmailDto> Emails { get; init; } = [];
+}
+#endif