NABATIEH, Lebanon — The city was once the second largest in southern Lebanon, a pulsing trade hub where tens of thousands packed into a centuries-old bazaar, apartment blocks, coffee shops, and a famed weekly farmers market. Over the years, it came to symbolize southern Lebanon’s prosperous rise since the end of a long civil war. Now, Nabatieh is deserted. Its streets are empty, its storefronts shuttered or mangled from airstrikes.