Proposal: Add Email/Password Authentication

[alexandrevilain]

Currently, Zola only supports Google OAuth for authentication. While convenient for many users, I personally prefer email/password authentication due to privacy concerns with Google integration and because it requires extra configuration steps when setting up the project for self-hosting.

Since the project uses Supabase, adding email/password authentication using Supabase's built-in auth capabilities should be straightforward.
However, this may overlap with #100 (NextAuth (or BetterAuth) + Drizzle refactor).

What do you prefer @ibelick? Implementing email/password auth as an interim solution, or should we start/wait for the BetterAuth/Drizzle refactor?

[ibelick]

I think we can wait for the project to be more stable and also to have more requests for a migration before starting one.

That said, it should be relatively easy to add email+password auth with supabase and I would be happy to review a PR for it.