Shanghai authorities urged residents to stay at home this weekend, seeking a toned-down Christmas in the nation’s most populous city as Covid-19 rages nationwide after tough curbs were lifted. A branch of the Shanghai Municipal Health Commission on Saturday urged young people in particular to avoid crowded gatherings, due to the ease of spreading the coronavirus and low temperatures. Christmas is not traditionally celebrated in China, but it is common for young couples and some families to spend the holiday together. The omicron variant is surging weeks after the authorities abruptly ended their zero-Covid policy, lifting strict testing requirements and...