ON A WEEKDAY morning in Lagos, somewhere between the time a customer downloads a fintech app and the moment she taps "deposit", her face is photographed, matched against a national identity database, scored for liveness, and either approved or rejected. The whole exchange takes a few seconds. It costs the fintech a few cents. Somewhere in the middle, a company called Smile Identity earns a tiny piece of the transaction. By early 2023, Smile had …