Fresh off his headline-making “Bieberchella” run in the desert, Justin Bieber reportedly performed a private set this week at Jeffrey Katzenberg’s ultra-exclusive WNDR conference in Montecito. On Thursday, May 7, Puck's Dylan Byers broke the news on X , sharing a copy of the conference agenda. Held over three days at the Rosewood Miramar , the annual top-secret event is invite-only for Fortune 100 CEOs, tech founders, and Hollywood A-listers. The 32-year-old “Peaches” singer's set went down Wednesday night, and he reportedly gave attendees permission to take photos — which is likely how images of the performance ended up circulating online, given that phones and cameras aren't normally allowed at the event.…