control-plane: fix deletion of old drafts

This commit fixes the migration for deleting old drafts, so that it can be
applied.  It was broken, and was thankfully never applied in production.

supabase/migrations/26_delete_old_drafts.sql

@@ -1,9 +1,11 @@
+begin;
 -- The purpose of this is to cleanup old drafts, draft_specs, discovers, and evolutions.
 -- These things can pile up over time, and there's no need to retain them for a long time.
 -- Note that the cleanup of draft_specs, discovers, and evolutions happens due to cascading
 -- deletions from drafts.
 
 -- We need to add the foreign key constraint to evolutions, since it was not there originally.
+delete from evolutions e where not exists (select d.id from drafts d where d.id = e.draft_id);
 alter table evolutions add foreign key (draft_id) references drafts(id) on delete cascade;
 
 create or replace function internal.delete_old_drafts()
@@ -16,9 +18,11 @@ returns bigint as $$
   select count(*) from d;
 $$ language sql security definer;
 
--- create extension if not exists pg_cron with schema extensions;
--- select cron.schedule(
--- 	'delete-drafts', -- name of the cron job
--- 	'0 15 * * *', -- Every day at 15:00Z (midmorning EST)
--- 	$$ delete from drafts $$
--- );
+create extension if not exists pg_cron with schema extensions;
+select cron.schedule(
+	'delete-drafts', -- name of the cron job
+	'0 15 * * *', -- Every day at 15:00Z (midmorning EST)
+	$$ select internal.delete_old_drafts() $$
+);
+
+commit;