-- Draw hardening (adversarial review fixes):
--   * persist the drand BLS signature so the published bundle is independently
--     re-verifiable (randomness = sha256(signature)).
--   * freeze the prize set (count + ids in position order) at commit so
--     verification is reproducible even if prizes are edited after the draw.
ALTER TABLE "draws" ADD COLUMN "snapshot_prize_count" integer;--> statement-breakpoint
ALTER TABLE "draws" ADD COLUMN "snapshot_prize_ids" jsonb;--> statement-breakpoint
ALTER TABLE "draws" ADD COLUMN "drand_signature" text;