Rename --block_private_networks to --block-private-networks and
--block_cidrs to --block-cidrs to match the existing flag naming
convention (e.g. --http-proxy, --proxy-bearer-token).
CIDRs prefixed with '-' are treated as allow rules that exempt matching
IPs from blocking. Allow rules take precedence over both
--block_private_networks and custom block CIDRs.
Example: --block_private_networks --block_cidrs -10.0.0.42/32
blocks all private ranges except 10.0.0.42.
Adds 3 new tests for allow-list behavior.
Block outbound HTTP requests to specified IP ranges before TCP handshake
using libcurl CURLOPT_OPENSOCKETFUNCTION callback. Fires after DNS
resolution, reads resolved IP directly from sockaddr, does bitwise CIDR
comparison. Fail-closed: unknown address families are blocked.
--block_private_networks blocks RFC1918, localhost, link-local, ULA.
--block_cidrs blocks additional comma-separated CIDRs.
IPv4-mapped IPv6 (::ffff:x.x.x.x) is unwrapped to prevent bypass.
