History in a recently created room is silently hidden from new members

### Description

Joining as a new user in a room with private room history, gives no indication that this is the case; the room just looks empty and dead.

From the perspective of someone already in the room:


And then from the perspective of a new user:


### Steps to reproduce

- Create a room that has history set to "members only from when they joined"
- Say something in the room
- Join from another user
- See an empty room, no history, nor any indication that history was elided

This *should* include a clear indicator that the room history is being hidden, so that the user understands that there may have been conversational history (and the room isn't dead), they just can't see it. Similar to how there's a clear "this room uses E2EE" indicator after joining it, really.

In fact, I'd argue that the "this is the start of the room" without an elided-history marker is actively misleading to users, as it almost explicitly says that there *isn't* something being elided!

Logs being sent: no

### Version information

- **Platform**: web/desktop, specific versions not relevant - it's just a missing feature