/s

Simplify IMAP email fetching API and refactor logic

Removed `markAsSeen` parameter from `FetchEmailsAsync` and
`FetchEmailByUidAsync` methods in `IImapEmailService` to
simplify the API. Updated `MailSearchFilter` to make `MaxCount`
nullable for greater flexibility.

Removed `markAsSeen` from `FetchEmailByUidQuery` and
`FetchEmailsQuery` records and their handlers. Deleted
`FetchEmailByUidQueryValidator` as it is no longer needed.

Refactored `LimilabsImapEmailService`:
- Introduced `FetchEmailUidsAsync` to centralize UID fetching logic.
- Simplified `FetchEmailByUidAsync` using a new helper method.
- Consolidated connection, authentication, and folder selection
  into reusable private methods.
- Removed redundant code for search criteria and flag fetching.

Removed `IsSeen` from `ReceivedEmailContext` and improved
overall code readability and maintainability by reducing
duplication and centralizing logic.

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

@@ -21,12 +21,6 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
     /// Mail query used to filter and limit the emails retrieved.
     /// </summary>
     public MailSearchFilter Mail { get; init; } = new();
-
-    /// <summary>
-    /// When <see langword="true"/> (default), fetched messages are marked as <c>\Seen</c> on the server.
-    /// Set to <see langword="false"/> for a non-destructive peek.
-    /// </summary>
-    public bool MarkAsSeen { get; init; } = true;
 }
 
 public class FetchEmailsQueryHandler(
@@ -46,7 +40,6 @@ public class FetchEmailsQueryHandler(
         return await ImapService.FetchEmailsAsync(
             account,
             request.Mail,
-            request.MarkAsSeen,
             cancellationToken);
     }
 }