Seeking to build a booking and management platform for both live and virtual fitness classes. Features should include: - User registration and management - Class browsing, booking, calendar integration - Stripe-powered payments - Instructor profiles and admin panel - Email notifications for signups, changes, and reminders - Next.js 14 + Tailwind for frontend - Node.js API and PostgreSQL backend - Must be mobile-first, Lighthouse 90+, secure, and well-documented Please link examples of similar platforms you've delivered.