Tailboot v2026.09.05.194107

Inject verified ISO config offset into browser customizer (#31)

* Inject verified ISO config offset into browser customizer

- Validate and test fixed-slot ISO patching against built images
- Pass the verified offset from release builds to the site

* Simplify ISO config offset handling

- Remove redundant raw-byte verification and documentation
- Streamline browser patcher comments

* Validate ISO config offset with Zod

- Add Zod as a site dependency
- Parse the release config offset as a nonnegative integer