Function refresh_queue_local_sources 

pub(super) async fn refresh_queue_local_sources(
    controller: &PlayerController,
    db: &DatabaseWrapper,
) -> Result<usize, String>

Re-point queued streaming items at completed local downloads.

Sources are resolved once when the queue is built, so downloads that finish while it plays (preloaded upcoming tracks) — or that existed before the connection dropped — would otherwise keep streaming. Called before advancing so the next track always prefers the on-disk copy.

Returns the number of items switched to a local source.