The wellness retreats travelers are flocking to right now are not gentle spa weekends. They are structured, results-driven programs with strict schedules, plant-based meals and no TVs — and the most talked-about of them, The Ranch Malibu, has quietly become Hollywood’s go-to reset destination. With a hard cap of 25 guests a week and nightly rates topping $1,500, it is part fitness boot camp, part luxury escape and entirely sold on the idea that …