DUBAI—Before the Iran war, 40,000 shipping containers a day moved through Jebel Ali port, a sprawling complex of deep-water piers and warehouses that powered this city-state’s rise from backwater to international powerhouse. Now, just 1,000 containers pass by the largely vacant docks. Port officials are racing to ramp back up to prewar traffic, but the reality, they say, is that it will take at least a month. It is the same across Dubai, the once-vibrant emirate of skyscrapers and strivers that unexpectedly found itself on the front lines of the Iran war. Dubai is at the beginning of a postwar…