Iran on Sunday allowed thousands of its Shia faithful to gather for one of the Islamic sect’s most important religious holidays, the latest attempt on the part of leaders to preserve a sense of normalcy even as the country grapples with high infection rates from coronavirus. Iran has struggled to contain the Covid-19 pandemic, which has killed more than 21,000 people in the country. Rather than keeping the country locked down, the government has sought to balance public-health concerns without strangling an economy battered…