TF-1831 Handle system back button in search email

Signed-off-by: dab246 <tdvu@linagora.com>

Signed-off-by: dab246 <tdvu@linagora.com>
(cherry picked from commit f4ffd113f192415c8613bf12fe40db1af902edaf)

lib/features/mailbox/presentation/action/mailbox_ui_action.dart

@@ -1,7 +1,7 @@
 
+import 'package:jmap_dart_client/jmap/core/state.dart' as jmap;
 import 'package:model/mailbox/presentation_mailbox.dart';
 import 'package:tmail_ui_user/features/base/action/ui_action.dart';
-import 'package:jmap_dart_client/jmap/core/state.dart' as jmap;
 
 class MailboxUIAction extends UIAction {
   static final idle = MailboxUIAction();
@@ -31,4 +31,6 @@ class OpenMailboxAction extends MailboxUIAction {
 
   @override
   List<Object?> get props => [presentationMailbox];
-}
+}
+
+class SystemBackToInboxAction extends MailboxUIAction {}