Renumber PXE LAN from 10.9.100.0/24 to 172.16.9.0/24

Single-site bay-stuck issue at WJ: GE Intune Report IP script filters
Get-NetIPAddress on StartsWith("10.") and posts everything matching
to the GE Tines webhook. Bays at WJ get the PXE LAN 10.9.100.x IP
captured and reported -> GE backend tags bays as on a non-corp 10.x
subnet -> dynamic group eligibility for SFLD policy never matches.
Other GE sites work because their PXE LANs aren't on 10.x at all.

Renumber PXE LAN to RFC1918 172.16.9.0/24 so the GE filter naturally
skips wired PXE addresses without any disable-NIC dance.

Server-side already in flight (netplan dual-bound, dnsmasq scope +
boot URL repointed, blancco preferences + grub.cfg + iPXE GetPxeScript
all sed'd to 172.16.9.1). This commit is the playbook / scripts /
docs side: 109 hits across 35 files sed'd in one shot.

After this lands + boot.wim is rebuilt + bays renumber off DHCP,
the 10.9.100.1 binding will be dropped from netplan as the final
cleanup step.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

webapp/templates/imaging.html

@@ -116,7 +116,7 @@
 <div class="card mt-3">
   <div class="card-body small text-muted">
     <strong>How to push status from an imaging client:</strong>
-    <pre class="mb-0 mt-2">POST http://10.9.100.1:9009/imaging/status
+    <pre class="mb-0 mt-2">POST http://172.16.9.1:9009/imaging/status
 Content-Type: application/json
 
 {