[Feature] Don't bother using public APIs on non-routable IP addresses

[OdinVex]

Web-Check currently tries to fetch Archive.org (and various other public API endpoints) even for non-routable IP addresses, eg. Class C IPv4 addresses and site-local fc00::/7 addresses. It's just a waste of bandwidth and will always return an error, so these tests should be skipped (provide the reason for skipping).

[sophymarine]

Our team ran into this exact loop back in March. Staging was leaking fc00::/7 and RFC 1918 blocks directly into external request logs. It exposes internal topology to third parties. That fails audits. We solved it by writing a quick subnet filter that drops the query before the HTTP library even sets up a socket. Are you planning to write a lightweight parser for these blocks, or are you pulling in an external helper to handle the validation?