Affected: PyPI: flyto-core

## Summary

`flyto-core`'s SSRF protection (`validate_url_ssrf` / `is_private_ip` in `src/core/utils.py`) blocks private and metadata destinations by resolving the host and testing the resulting IP for membership in a hardcoded `PRIVATE_IP_RANGES` list. That list contains only the *native* RFC 1918 / loopback / link-local / unique-local ranges. It does **not** account for IPv6 transition address forms that embed an IPv4 (or loopback) target:

- IPv4-mapped `::ffff:a.b.c.d` - IPv4-compatible `::a.b.c.d` - 6to4 `2002::/16` - NAT64 well-known prefix `64:ff9b::/96` and local-use `64:ff9b:1::/48`

A workflow author can submit a URL with a literal transition-form host (for example `http://[::ffff:127.0.0.1]:8080/...` or `http://[64:ff9b::a9fe:a9fe]/latest/meta-data/`). `is_private_ip()` returns `False` for these (the address is not literally inside any listed range), so `validate_url_ssrf` lets the request through, and the `http.get` atomic module (and ~10 sibling modules that share the same guard) performs the outbound `aiohttp` fetch and returns the response body. On a host that uses NAT64/6to4 these addresses route to the embedded IPv4 endpoint (e.g. the cloud instance-metadata service `169.254.169.254`); on any dual-stack host the IPv4-mapped form is routed by the kernel directly to the embedded IPv4, including loopback and RFC 1918 internal services.

This is CWE-918 (Server-Side Request Forgery): the guard that exists specifically to keep workflow-authored URLs away from int…