Function queue_unsynced_files 

pub async fn queue_unsynced_files(
    watch_paths: Vec<WatchPathEntry>,
    queue_manager: Arc<QueueManager>,
    sync_index: Arc<ShardedSyncIndex>,
    api_client: Arc<ImmichApiClient>,
    catchup_mode: StartupCatchupMode,
    shared_state: Arc<Mutex<AppState>>,
    app_ctx: Arc<AppContext>,
)

Scans watch folders at startup and queues new, changed, or retargeted files for upload.

Stage 1 parallelises the directory walk and filtering via rayon. Stage 2 resolves album IDs and processes candidates with bounded async concurrency.