By Brenda Goh and Martin Quin Pollard SHANGHAI/BEIJING (Reuters) – Shanghai reopened a small part of the world’s longest subway system on Sunday after some lines had been closed for almost two months, as the city paves the way for a more complete lifting of its painful COVID-19 lockdown next week. With most residents not allowed to leave their homes and restrictions tightening in parts of China’s most populous city, commuters early on Sunday needed strong reasons to travel. Shanghai’s lockdown and curbs in other cities have battered consumption, industrial output and other sectors of the Chine…