Applog heartbeat dormant - blocked on coder-venus-cc's shared writer-script appKey fix

VENUS-378 applog heartbeat: applog_writer role minted on eprpywqwzsvrjeaforei by db-enamel-cc (courtesy, not GO-scope - least-priv, no shared-table structural change), verified live (LOGIN, INSERT-only on appEvents). DSN wired into terra.env on venus. NOT activated: shared heartbeat-writer script omits appKey on every insert (blocks enamel's own wiring too), routed to coder-venus-cc by db-enamel-cc. Terra's leg closes once that ships and a live heartbeat row with appKey=terra reads back.