Create protected route for image generation

[LauraBeatris]

The route for image generation should be protected, therefore only authenticated users with a valid cookie should be able to access it.

Atm there's a draft boilerplate for authentication with Authkit, but it should be refactored to handle the protected route case.

Refer to the Authkit repo as an example: https://github.com/workos/authkit

[yazaldefilimone]

Hello @LauraBeatris, are you doing it? Or can I try to do it?

[LauraBeatris]

Hey @yazaldefilimone! This has already landed on https://github.com/LauraBeatris/starry/commit/2a73896410a611bad1eb6ce0872275eb7a3fa2de