fix: update iptables binary paths to use /usr/sbin instead of /sbin

Standardize iptables paths across firewall scripts and Go code to ensure compatibility with systems where iptables is located in /usr/sbin. This affects both legacy and non-legacy iptables binaries.

firewall/firewall-add

@@ -407,7 +407,7 @@ for source_ip_index in $(seq 1 $COUNT_SOURCE_IP); do
                 if [[ "$PREROUTING" == "true" ]] || [[ "$POSTROUTING" == "true" ]] || [[ "$HOST" == "true" ]]; then
 
                     if [ "$HOST" == "true" ]; then
-                        IPTABLES="/sbin/iptables -t nat"
+                        IPTABLES="/usr/sbin/iptables -t nat"
                         debug "iptables: "$IPTABLES
                     else
                         IPTABLES="nsenter -t $(docker inspect --format {{.State.Pid}} $NAME) -n -- /sbin/iptables-legacy -t nat"