Function maybe_first_time_setup 

pub fn maybe_first_time_setup(chat: &Arc<Container>) -> bool

If first-time setup hasn’t run yet, show a brief setup note + the earendil announcement in the chat container. The TS original is a multi-step dialog (theme picker, analytics opt-in); this v1 simplifies to a one-shot banner

• the theme remains pickable via /theme. Analytics is deferred (no telemetry wiring). Returns true if anything was shown.