Function update_settings 

pub async fn update_settings(
    scheduler: State<'_, Scheduler>,
    supporter_state: State<'_, SupporterAppState>,
    new: Settings,
) -> Result<(), String>

Replace the active profile’s settings with new and persist.

Hook fields are stripped from the payload before merge (see strip_hooks) — hooks must go through set_hooks so the user confirmation dialog can fire. custom_css is gated the same way: non-supporters can’t change it (we substitute the previously-persisted value), and the value gets sanitised + clamped before write. Returns when the write hits disk.