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/presentation/DigitalData.MessagingService.API/Controllers/EmailController.cs

@@ -94,22 +94,22 @@ public class EmailController(IMediator mediator) : ControllerBase
     [ProducesResponseType(StatusCodes.Status404NotFound)]
     public async Task<IActionResult> FetchEmails([FromQuery] ReadEmailQuery query, [FromQuery] OnlyFilter? only = null, CancellationToken cancellationToken = default)
     {
-        var emails = await mediator.Send(query, cancellationToken);
+        var res = await mediator.Send(query, cancellationToken);
 
-        if(!emails.Any())
+        if(!res.Emails.Any())
             return NotFound("No emails found matching the specified criteria.");
 
         if (only == OnlyFilter.HtmlBody)
         {
-            if (emails.FirstOrDefault()?.HtmlBody is string htmlBody)
+            if (res.Emails.FirstOrDefault()?.HtmlBody is string htmlBody)
                 return Content(htmlBody, "text/html");
             else
                 return NotFound();
         }
         else if (only == OnlyFilter.Uid)
-            return Ok(emails.Select(e => e.Uid).ToList());
+            return Ok(res.Emails.Select(e => e.Uid).ToList());
         else
-            return Ok(emails);
+            return Ok(res);
     }
     #endregion Receive
 }