Remove caching from LimilabsImapEmailService

Simplified the `LimilabsImapEmailService` by removing the dependency on `IMemoryCache` and eliminating all caching logic. The constructor no longer accepts an `IMemoryCache` parameter, and the static `CacheKeyPrefix` field has been removed.

Replaced the caching mechanism with direct email fetching using `imap.GetMessageByUIDAsync`. Refactored the logic for processing attachments and visuals into `EmailAttachmentDto` objects, and streamlined the construction of `ReceivedEmailDto` to include metadata directly from the fetched email data.

These changes reduce complexity, improve maintainability, and ensure the service always retrieves the latest email data from the IMAP server.

src/infrastructure/DigitalData.MessagingService.Infrastructure/Services/LimilabsImapEmailService.cs

@@ -6,7 +6,6 @@ using DigitalData.MessagingService.Domain.Exceptions;
 using DigitalData.MessagingService.Infrastructure.Services.Extensions;
 using Limilabs.Client.IMAP;
 using Limilabs.Mail;
-using Microsoft.Extensions.Caching.Memory;
 using Microsoft.Extensions.Logging;
 using System.Text;
 
@@ -16,10 +15,8 @@ namespace DigitalData.MessagingService.Infrastructure.Services;
 /// IMAP email service using Limilabs Mail.dll.
 /// Opens a fresh connection per call — stateless and thread-safe.
 /// </summary>
-public class LimilabsImapEmailService(ILogger<LimilabsImapEmailService> Logger, IMemoryCache Cache) : IImapEmailService
+public class LimilabsImapEmailService(ILogger<LimilabsImapEmailService> Logger) : IImapEmailService
 {
-    private static readonly string CacheKeyPrefix = Guid.NewGuid().ToString();
-
     static LimilabsImapEmailService()
     {
         Encoding.RegisterProvider(CodePagesEncodingProvider.Instance);
@@ -67,10 +64,6 @@ public class LimilabsImapEmailService(ILogger<LimilabsImapEmailService> Logger,
                 try
                 {
                     #region Read email
-                    var email = await Cache.GetOrCreateAsync(
-                        CacheKeyPrefix + uid,
-                        async entry =>
-                        {
                     var eml = await imap.GetMessageByUIDAsync(uid, cancel);
                     var mail = new MailBuilder().CreateFromEml(eml);
                     var flags = await imap.GetFlagsByUIDAsync(uid, cancel);
@@ -101,7 +94,7 @@ public class LimilabsImapEmailService(ILogger<LimilabsImapEmailService> Logger,
                         });
                     }
 
-                            return new ReceivedEmailDto
+                    var email = new ReceivedEmailDto
                     {
                         Uid = uid,
                         From = mail.From.FirstOrDefault()?.Address ?? string.Empty,
@@ -114,12 +107,8 @@ public class LimilabsImapEmailService(ILogger<LimilabsImapEmailService> Logger,
                         IsSeen = flags.Contains(Flag.Seen),
                         Attachments = attachments,
                     };
-                        });
                     #endregion Read email
 
-                    if (email is null)
-                        continue;
-
                     if (filter.UnseenOnly && email.IsSeen)
                         continue;