Function sync_full_catalog 

pub async fn sync_full_catalog(
    repository: State<'_, RepositoryManagerWrapper>,
    db: State<'_, DatabaseWrapper>,
    handle: String,
) -> Result<CatalogSyncResult, String>

Walk every library on the server and persist all items to the offline cache so the full catalog is browsable offline (greyed out when not downloaded).

Best-effort: a library that fails to fetch is counted and skipped rather than aborting the whole sync. Runs libraries sequentially to avoid hammering the server. Uses Recursive=true so a single request per library returns the containers and their playable children.