Ensure Zod validation and deserialization of credentials is future-proof

[mitschabaude]

With recent additions to credentials serialization, Zod validation on the Pallad PR is now failing, maybe because the serialization of some type changed or new types were added that aren't understood yet.

This incident makes it clear that we have to be extremely mindful of stability of serializations going forward, since it won't be possible to change the version of either mina-attestations or o1js baked into wallets very often.