chore(api): anchor the seeded demo character's HP regeneration

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/src/database/seeds/vertical-slice.seed.ts

@@ -243,6 +243,7 @@ export async function seedVisibleVerticalSlice(
       baseHp: 100,
       baseAttack: 6,
       currentHp: 100,
+      hpRegenSince: new Date(),
       currentLocationId: southGateId,
     });
   }