Migrate from 3rd party canonicalization lib to zk-email-verify helpers

[foolo]

Currently we use https://www.npmjs.com/package/dkim in src/app/api/gmail/route.ts
https://github.com/zkemail/archive.prove.email/blob/main/src/lib/store_email_signature.ts#L18

Migrate to zk-email-verify
https://github.com/zkemail/zk-email-verify/blob/main/packages/helpers/src/lib/mailauth/dkim-verifier.ts#L184

Blocked by pending updates related to quotable printable encoding in zk-email-verify, and after that, may need to refactor the code in zk-email-verify to expose a canonicalization function that can be used in a modular way.