Conversations on files displayed as public

Steps to reproduce

1. Make sure to enable Conversations on files in /settings/admin/talk
2. In Nextcloud files, open the details sidebar of a shared file and select Chat -> Join Conversation
   -> A conversation is created and displayed in the sidebar.
3. In Nextcloud talk, open that conversation and open the conversation settings.
4. Under Moderation, "Guests are allowed to join this conversation via link" is activated and cannot be changed.
5. Copy the Guest Link, try it in a private browser window and see how it is not working (which is good).

Expected behaviour

The conversation should not be displayed as public.

Actual behaviour

The conversation should display as a "normal" (non-public) conversation and the link should work, but only as a normal, internal link, that can be opened just by logged-in users to join the conversation.

Talk app

Talk app version: 21.1.5

Nextcloud

** Nextcloud Server version:** 31.0.9

Reproduce the flow from Nextcloud Files' details sidebar to Talk conversation settings, focusing on the Moderation option and Guest Link behavior. Trace how the conversation created through Conversations on files is classified, then verify that it is shown as normal and that its internal link is usable only by logged-in users.