Fix: UFW IPv4 Rules Not Applied to IPv6

UFW manages both IPv4 (iptables) and IPv6 (ip6tables), but IPv6 rules are only applied when IPV6=yes is set in /etc/default/ufw.

IPV6=yes

sudo ufw disable && sudo ufw enable
# Verify:
sudo ip6tables -L INPUT | grep -E "ACCEPT|DROP|REJECT"