Function extend_corpus_human 

pub fn extend_corpus_human(
    name: &str,
    session: Option<AdminSession>,
    pool: &State<DbPool>,
    database_url: &State<DatabaseUrl>,
) -> Result<Redirect, Status>

The human twin of extend_corpus: the corpus screen’s “Re-scan for new entries” button. Gated by the signed-in AdminSession cookie (anonymous → sign-in); spawns the extend job and redirects to /jobs. 404 if the corpus is unknown.