fix schema migration

backend/migrations/000003_balanceall_enemies.sql

@@ -1,6 +1,13 @@
 -- Enemy combat stats from balanceall grid (tiered targets, DoT-aware path for burn/poison).
 -- fire_demon: tuned with burn enabled (grid dot branch in cmd/balanceall).
 
+-- Older init snapshots may lack per-level columns; align with current schema before UPDATEs.
+ALTER TABLE public.enemies ADD COLUMN IF NOT EXISTS hp_per_level double precision DEFAULT 6.0 NOT NULL;
+ALTER TABLE public.enemies ADD COLUMN IF NOT EXISTS attack_per_level double precision DEFAULT 1.8 NOT NULL;
+ALTER TABLE public.enemies ADD COLUMN IF NOT EXISTS defense_per_level double precision DEFAULT 1.5 NOT NULL;
+ALTER TABLE public.enemies ADD COLUMN IF NOT EXISTS xp_per_level double precision DEFAULT 2.0 NOT NULL;
+ALTER TABLE public.enemies ADD COLUMN IF NOT EXISTS gold_per_level double precision DEFAULT 1.2 NOT NULL;
+
 UPDATE enemies SET hp = 94, max_hp = 94, hp_per_level = 7.8681, attack = 20, attack_per_level = 2.7054 WHERE type = 'wolf';
 UPDATE enemies SET hp = 102, max_hp = 102, hp_per_level = 8.2826, attack = 25, attack_per_level = 2.3190 WHERE type = 'boar';
 UPDATE enemies SET hp = 107, max_hp = 107, hp_per_level = 6.9412, attack = 28, attack_per_level = 2.5898 WHERE type = 'zombie';