Refactor FetchEmailsQuery and improve UID handling

Moved the `Folder` property from `FetchEmailsQuery` to the
`MailQuery` record to better encapsulate query parameters.
Updated `FetchEmailsQueryHandler` to use `MailQuery.Folder`
for improved modularity. Simplified UID limiting logic in
`LimilabsImapEmailService` by replacing `Take().ToList()`
with the more concise `[.. Take()]` syntax.

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

@@ -16,11 +16,6 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
     /// </summary>
     public required GetSenderQuery Account { get; init; }
 
-    /// <summary>
-    /// Mailbox folder to read from (default: "INBOX").
-    /// </summary>
-    public string Folder { get; init; } = "INBOX";
-
     /// <summary>
     /// Mail query used to filter and limit the emails retrieved.
     /// </summary>
@@ -28,6 +23,11 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
 
     public record MailQuery
     {
+        /// <summary>
+        /// Mailbox folder to read from (default: "INBOX").
+        /// </summary>
+        public string Folder { get; init; } = "INBOX";
+
         /// <summary>
         /// When <see langword="true"/> returns only unread messages.
         /// </summary>
@@ -56,7 +56,7 @@ public class FetchEmailsQueryHandler(
 
         return await ImapService.FetchEmailsAsync(
             account,
-            request.Folder,
+            request.Mail.Folder,
             request.Mail.UnseenOnly,
             request.Mail.MaxCount,
             cancellationToken);

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

@@ -44,7 +44,7 @@ public class LimilabsImapEmailService(
             // Most-recent first; honour maxCount
             uids.Reverse();
             if (maxCount > 0 && uids.Count > maxCount)
-                uids = uids.Take(maxCount).ToList();
+                uids = [.. uids.Take(maxCount)];
 
             var results = new List<ReceivedEmailContext>(uids.Count);