homepage: polish pass (C)

services.yaml:
- ANA-Firewall: href + siteMonitor both point at the IP now (was href
  to FQDN but siteMonitor to IP — inconsistent)
- PFI-VM-Docker, NH3-SW1, NH3-VM-Docker, ESH-VM-Docker: upgrade from
  `ping:` to `siteMonitor:` against the href URL so the up/down dot
  reflects whether the web UI actually responds, not just ICMP

dockge canonical:
- icon sh-dockge.png (was si-portainer — wrong project). Applies to all
  five fleet Dockge instances once their compose files are redeployed.

Per-group colors investigated but not supported by homepage (only site-
wide `color:` exists); skipped.

stacks/dockge/compose.yaml

@@ -24,7 +24,7 @@ services:
     labels:
       - homepage.group=Service Networking
       - homepage.name=Dockge (${DOCKGE_HOST_LABEL})
-      - homepage.icon=si-portainer
+      - homepage.icon=sh-dockge.png
       - homepage.description=Compose UI on ${DOCKGE_HOST_LABEL}
       - homepage.href=http://${DOCKGE_HOST_IP}:${DOCKGE_PORT:-5001}