Overall, really solid start on your design docs! Here are my notes so far:
MVP LIST
[ ] Which features can a user use when logged out? What is restricted to being logged in?
[ ] Homepage (or splash page) will be part of auth, so you should remove this as its own MVP. When building this, you'll just neglect the lessons index at first, and then finishing building it out during the Lessons MVP.
[ ] Add production README as MVP 7
SCHEMA
[ ] Photos will be attached using activestorage which will build its own tables, so you can remove all foreign keys referencing photos
[ ] Will lessons be in categories (as they are on instructables)? If so, you'll need to add a table of categories and a foreign key on lessons to point to the categories table.
Overall, really solid start on your design docs! Here are my notes so far: MVP LIST
SCHEMA