Add exported isBlockedAddress(ip) helper covering loopback, 0.0.0.0,
private v4 (10/8, 172.16-31, 192.168/16), link-local (169.254/16,
fe80::/10), and IPv6 ULA (fc00::/7). In fetchUrl, after the existing
literal-hostname fast-reject, resolve the hostname via dns.lookup
(all:true) when using the real fetcher and block if any resolved
address isBlockedAddress. Injected fetcher (tests) skips DNS.
Drop unused contentType from return value.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
086bd1e6a3