fix: seed demo users on startup

entrypoint.sh

@@ -6,5 +6,8 @@ cd backend
 # db push avoids broken migration issues on ephemeral containers
 npx prisma db push --accept-data-loss
 
+echo "[entrypoint] Seeding demo users..."
+node prisma/seed.js
+
 echo "[entrypoint] Starting PolySignal server..."
 exec node src/index.js