fleet: retire NH3-Firewall (Fortigate 101F @ 10.100.250.1)

Device has been removed from the NH3 site. Drop the homepage card
and the corresponding example in discover-fortigate.sh.

Note left in services.yaml so whoever adds the replacement edge
device knows where the old entry lived.

configs/homepage/services.yaml

@@ -90,11 +90,8 @@
       description: BMC (ana-ml2)
 
 - Infra - NH3:
-  - NH3-Firewall:
-      href: https://10.100.250.1
-      icon: mdi-wall-fire
-      siteMonitor: https://10.100.250.1
-      description: nh3-gw Fortigate 101F
+  # NH3-Firewall (Fortigate 101F at 10.100.250.1) retired 2026-04-21 —
+  # re-add if/when a new edge device is installed.
   - NH3-SW1:
       href: https://10.100.250.2
       icon: mdi-switch

scripts/discover-fortigate.sh

@@ -17,7 +17,6 @@
 #
 # Example:
 #   scripts/discover-fortigate.sh ana-fw.phasefinal.com > leases-ana.tsv
-#   scripts/discover-fortigate.sh nh3-gw.phasefinal.com > leases-nh3.tsv
 #
 # Requires: ssh config (or `~/.ssh/config` host alias) for the FortiGate,
 # with key auth OR interactive password. FortiGate's SSH expects admin-level