Refactor email search with new filter models

Replaced the old `SearchFilter` with the new `MailSearchFilter` model to enable more flexible and granular email search criteria. Introduced `DateFilter`, `UidFilter`, and `MailSortOrder` to support advanced filtering options such as date ranges, UID ranges, and sorting order. Updated `IImapEmailService` and `FetchEmailsQuery` to use the new models.

Added validators (`DateFilterValidator`, `MailSearchFilterValidator`, `UidFilterValidator`) to ensure input correctness. Refactored `LimilabsImapEmailService` to dynamically construct IMAP search queries based on the new filter properties, supporting unseen messages, text filters, and client-side attachment filtering.

Improved maintainability and scalability by cleaning up redundant code and leveraging the new models and validation framework.

src/core/DigitalData.MessagingService.Application/Common/Interfaces/IImapEmailService.cs

@@ -1,4 +1,5 @@
 using DigitalData.MessagingService.Abstraction;
+using DigitalData.MessagingService.Application.Common.Models.MailSearch;
 
 namespace DigitalData.MessagingService.Application.Common.Interfaces;
 
@@ -15,7 +16,7 @@ public interface IImapEmailService
     /// <param name="cancellationToken">Cancellation token.</param>
     Task<IEnumerable<ReceivedEmailContext>> FetchEmailsAsync(
         EmailAccountDto account,
-        FetchEmailsQuery.SearchFilter filter,
+        MailSearchFilter filter,
         CancellationToken cancellationToken = default);
 
     /// <summary>