Testimonials on /todo-cards, /newsletter, /challenge now come from the new
Payload testimonials collection via a shared TestimonialsGrid component,
instead of 3 separately hardcoded arrays.
Adds Next.js Draft Mode (/api/preview) plus Live-Preview-aware client
wrappers (LiveRichText, LiveTestimonialsGrid, LivePostContent) for posts,
legal pages, and testimonials — mounted only while Draft Mode is enabled,
so ordinary visitors keep getting the plain static components.
Marco