STOCKHOLM (Reuters) -H&M surprised investors on Wednesday with a new CEO, Daniel Erver, taking the role with immediate effect as the Swedish fashion retailer struggles to boost sales in a fiercely competitive market. Outgoing CEO Helena Helmersson said she decided to step down and leave H&M, saying the role has been very personally demanding. H&M, the world’s second-biggest fashion retailer, has struggled with its price-sensitive customers going to budget-friendly newcomer SHEIN in addition to competition from Inditex’s Zara. H&M’s fourth-quarter operating profit margin fell to 7.2%from 7.8% i…