Refactor IMAP email fetching to use SearchFilter

Replaced individual parameters (`folder`, `unseenOnly`, `maxCount`) in `IImapEmailService` with a consolidated `SearchFilter` object to simplify method signatures and improve maintainability.

Renamed `MailQuery` to `SearchFilter` in `FetchEmailsQuery` for better clarity. Updated `FetchEmailsQueryHandler` and `LimilabsImapEmailService` to use the new `SearchFilter` object, ensuring consistent handling of folder selection, unread message filtering, and message count limits.

Improved logging in `LimilabsImapEmailService` to reflect the updated `SearchFilter` structure.

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

@@ -19,9 +19,9 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
     /// <summary>
     /// Mail query used to filter and limit the emails retrieved.
     /// </summary>
-    public MailQuery Mail { get; init; } = new();
+    public SearchFilter Mail { get; init; } = new();
 
-    public record MailQuery
+    public record SearchFilter
     {
         /// <summary>
         /// Mailbox folder to read from (default: "INBOX").
@@ -56,9 +56,7 @@ public class FetchEmailsQueryHandler(
 
         return await ImapService.FetchEmailsAsync(
             account,
-            request.Mail.Folder,
-            request.Mail.UnseenOnly,
-            request.Mail.MaxCount,
+            request.Mail,
             cancellationToken);
     }
 }