Refactor email fetching methods in Limilabs service

Removed public methods `FetchEmailUidsAsync` and `FetchEmailByUidAsync` from `LimilabsImapEmailService` to simplify the public API.

Refactored `FetchEmailUidsAsync` into a private static helper method that operates directly on an `Imap` instance.

Removed exception handling logic specific to the removed methods. These changes aim to encapsulate email fetching functionality and streamline the service's design.

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

@@ -79,62 +79,6 @@ public class LimilabsImapEmailService(
         }
     }
 
-    public async Task<IEnumerable<long>> FetchEmailUidsAsync(
-        EmailAccountDto account,
-        MailSearchFilter filter,
-        CancellationToken cancellationToken = default)
-    {
-        using var imap = await OpenAsync(account, filter.Folder);
-        try
-        {
-            List<long> uids = await FetchEmailUidsAsync(imap, filter, cancellationToken);
-
-            await imap.CloseAsync(cancellationToken);
-            return uids;
-        }
-        catch (Limilabs.Client.ServerException ex)
-        {
-            await imap.CloseSafelyAsync();
-            throw new AuthenticationFailedException(
-                $"IMAP authentication failed for account '{account.Username}'.", ex);
-        }
-        catch (Exception ex) when (ex is not OperationCanceledException)
-        {
-            await imap.CloseSafelyAsync();
-            throw new InvalidOperationException(
-                $"Failed to fetch email UIDs from IMAP server '{account.ImapServer}'.", ex);
-        }
-    }
-
-    public async Task<ReceivedEmailContext?> FetchEmailByUidAsync(
-        EmailAccountDto account,
-        long uid,
-        string folder = "INBOX",
-        bool withAttachments = false,
-        CancellationToken cancellationToken = default)
-    {
-        using var imap = await OpenAsync(account, folder);
-        try
-        {
-            var mail = await FetchEmailByUidAsync(imap, uid, withAttachments, cancellationToken);
-
-            await imap.CloseAsync(cancellationToken);
-            return mail;
-        }
-        catch (Limilabs.Client.ServerException ex)
-        {
-            await imap.CloseSafelyAsync();
-            throw new AuthenticationFailedException(
-                $"IMAP authentication failed for account '{account.Username}'.", ex);
-            }
-        catch (Exception ex) when (ex is not OperationCanceledException)
-            {
-            await imap.CloseSafelyAsync();
-            Logger.LogWarning(ex, "Failed to fetch IMAP message UID={Uid} from folder {Folder}.", uid, folder);
-            return null;
-            }
-        }
-
     public async Task MarkAsSeenAsync(
         EmailAccountDto account,
         long uid,
@@ -162,7 +106,7 @@ public class LimilabsImapEmailService(
     }
 
     // Private helpers
-    private async Task<List<long>> FetchEmailUidsAsync(
+    private static async Task<List<long>> FetchEmailUidsAsync(
         Imap imap,
         MailSearchFilter filter,
         CancellationToken cancellationToken = default)