Function recents_clear 

pub async fn recents_clear(
    handle: State<'_, RecentsHandle>,
) -> Result<(), AppError>

Clear all recent locations and flush the empty list to disk.

Propagates the flush failure so the frontend’s clearMutation.onError can surface it. Previously the flush was swallowed and a disk error would silently leave the on-disk list intact — the next launch would reload the “cleared” entries.