Wire register and login forms to TanStack Form and generated Zod

[ExtraToast]

What to build

The register and login forms validate from the generated schemas, and the hand-written duplicates are deleted.

The spec already carries every structural rule those hand-written schemas restate — the username length bounds and pattern, the email format, the password minimum. What it cannot carry is the password-confirmation rule and the wording, so the form supplies exactly those two things and nothing else.

One consequence worth knowing before wiring this up: the generated client validates outbound request bodies too, so a submission that violates the contract fails before it reaches the network.

Acceptance criteria

• Both forms derive their structural rules from the contract
• Cross-field rules and estate-standard wording still apply
• The hand-written schema files are deleted
• Server-side validation failures still map onto the right fields

Blocked by

• Add withEstateMessages and the TanStack Form v1 peer
• Move every auth-ui operation onto the globally configured client