Banks in the European Union should quarantine their risky trading activities from their everyday savings and lending operations, as a way to safeguard the financial system and avoid future bailouts at taxpayers’ expense, a panel of financial experts recommended Tuesday. The recommendation, from a group led by the Bank of Finland’s governor, in some ways recalls the old Glass-Steagall Act in the United States, which for decades after the 1929 stock market crash kept stock trading and other investment banking activities separate from retail lending.