Add IPv6 private address support

[malston]

Summary

The IP detection logic doesn't properly handle IPv6 addresses or their private ranges.

Current Behavior

The extractDomain() function in src/utils/extractDomain.js only handles IPv4 private ranges (RFC 1918).

Expected Behavior

Should also detect IPv6 private/local ranges:

• fc00::/7 - Unique local addresses
• fe80::/10 - Link-local addresses

Priority

Medium

Related

Split from #3 (item #7)