Map (geocode) a batch of workspace addresses for Nearby — on demand

Admin-only, because each address is a BILLED Google Geocoding call (~$5 per 1,000), charged once per address and then cached forever. There is deliberately no scheduled job; an operator triggers this. Capped at MAX_PER_REQUEST per call so the request finishes inside gateway timeouts — the response reports remaining so the caller can simply call again. Idempotent: addresses already mapped, or already known unplaceable, are skipped and never re-billed.