Get Engine LCU consumed during the free trial

Returns the org-wide sum of priced Engine LCU consumed strictly before the GA cutoff (2026-06-01 UTC), i.e. all usage that was free, plus the count of projects that had Engine configured. Used to show admins how much they would have been billed and across how many projects when deciding whether to continue. The LCU value is Postgres-only (no in-flight Redis merge) since the post-cutoff modal shows after all pre-cutoff usage is swept.