Implement auth and basic create-read operations

[etareduction]

The shader body validation is missing (let's discuss that in separate issue), but basic DB structure with parent-child shader relations and stuff is here.

Also contains some N+1 problems with children shader authors and stuff, I'll open an issue for batching implementation.

But we can already discuss the schema and maybe start figuring out client side that uses it.

P.S. Sorry for the commit history, rebase might have been a mistake. Let's squash that.

[Lutymane]

Noice, but revert latest 2 commits, you merged index.html incorrectly

[Lutymane]

@etareduction also made a discussions topic for more convenience https://github.com/zeokku/glsl.app/discussions/4