Function run 

pub fn run(
    db: &Db,
    library_id: i64,
    home: &Path,
    settings: &ImportSettings,
    hub: &Sender<Event>,
    notif_id: ViewId,
    shutdown: &ShutdownSignal,
)

Runs a full directory scan and syncs the database for one library.

Sends pinned progress notifications to hub via notif_id while running. Checks shutdown between entries and exits early if shutdown is requested. On completion or early exit, closes the notification and returns.