Show dialog for permanently undownloadable attachments

ts/types/AttachmentNotAvailable.ts

@@ -0,0 +1,10 @@
+// Copyright 2025 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export enum AttachmentNotAvailableModalType {
+  File = 'File',
+  LongText = 'LongText',
+  Sticker = 'Sticker',
+  VisualMedia = 'VisualMedia',
+  VoiceMessage = 'VoiceMessage',
+}