Replace Joi validation with zod

[danielemery]

zod is quickly becoming the leading option in the validation library space (when Typescript is in play).

Originally it was planned to support multiple forms of validation (rather than only Joi like now). However the complexity in providing separate Dockerfiles etc for each doesn't seem worth it.

Instead we should replace the Joi with zod and put plans to support other options (like Joi and yup) on hold until when/if the project is adoped.