Support `zod/v4` in `@farfetched/zod`

Since Zod v4 has been released in May, can we please add support for `zod/v4` in `zodContract`?

The best option for the time being would be to expose both `v3` and `v4` import paths just like Zod does, to allow people to migrate.
This would require the minimum peer dependency to be bumped to `^3.25.0` from current `^3.19.0`.

References:
- Zod v4 announcement: https://zod.dev/v4
- `zod/v3` vs. `zod/v4` versioning: https://github.com/colinhacks/zod/issues/4371