Fixed auth, added login, focused on content.

Continuing where I left off yesterday. I need to fix the frontend auth issues and set it up so logging in is required to view all courses.

Took me much longer than I expected, but it's finally done:

• All courses except the demo now require signing up
• There is a "Demo The Course" button on the landing page

I set up the Reddit ads to run for a few days. They don't bring much, but it's something to give me some data to work with.

The main focus is now again on the content. Tomorrow.