fix(pxe-boot): use current pxe-boot IP (.247) in dnsmasq until Stage 5 renumber

vars.pxeServerIp was already set to the post-renumber target (.223) but the
pxe-boot CT is still at .247, so dnsmasq was advertising .223 as the TFTP server
and the VM couldn't reach it.  Update to .247 so PXE boot works now; the comment
reminds us to flip it back to .223 when Stage 5 step 6 renumbers the CT.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

variables.nix

@@ -4,7 +4,7 @@
   homeDomain = "sweet.home"; # base LAN domain for service subdomains (pve., docker.)
   tailnetDomain = "tail13f623.ts.net"; # Tailscale MagicDNS suffix
   lanCidr = "192.168.2.0/24"; # LAN subnet
-  pxeServerIp = "192.168.2.223"; # pxe-boot host's LAN IP
+  pxeServerIp = "192.168.2.247"; # pxe-boot host's LAN IP (update to .223 when Stage 5 step 6 renumbers the CT)
   pbsIp = "192.168.2.244"; # Proxmox Backup Server LAN IP
   domainControllerIp = "192.168.2.253"; # FreeIPA domain controller / primary DNS