Function player_local_media_path 

pub async fn player_local_media_path(
    db: State<'_, DatabaseWrapper>,
    item_id: String,
) -> Result<Option<String>, String>

The on-disk path for a downloaded item, for playback surfaces that resolve their own source rather than going through the queue.

The video player is the reason this exists: audio has preferred local files since queue construction, but video asks the repository for a stream URL and never consults downloads, so a downloaded film was still streamed — costing bandwidth that had already been spent and failing outright when offline.

Returns None when nothing is downloaded or the file is missing, so the caller falls back to streaming.

TRACES: UR-071 | DR-123 | UT-116