get_firewall_rules read searchRule but dropped the rule's gateway. A pass
rule with a gateway hands what it matches to that gateway, local
destinations included, so it does not reach a host on another internal
network. Without the field a caller judging reachability reads a rule meant
for internet traffic as a hole into every server: on the first real box,
"pass UDP IOT -> any" via WAN_GW made 61 hosts look reachable from the IoT
segment (netOrk #575).
The rule dict gains "gateway", the gateway's name or "". It is an extra
field like floating and interface_label; the generic diff compares a fixed
field list and ignores it.
