Mini course platform

Build a course delivery site for a solo instructor.

Core features:
1. Courses with modules and lessons (video, markdown, quiz)
2. Purchase via Stripe unlocks the course
3. Student view: progress bar, next lesson, downloads
4. Instructor dashboard: enrollments, revenue, completion
5. Certificates on completion

Data: courses, modules, lessons, enrollments, progress.
Must-haves: signed video URLs, resume where left off, drip schedule.