Resale alerts. Proxy services. Secret WhatsApps. This is what it takes to buy the best—and most coveted—clothes. The White Stripes’ anthem “Seven Nation Army” never fails to have a Proustian effect on Bianca Jebbia. Every time she hears it, Jebbia flashes back to the first time she walked into the Marni boutique on Mercer Street in New York. More than two decades later, she recalls entering a futuristic gallery of fashion, with clothes suspended from chrome rails as seriously