Remove dhcp-ignore filter to debug proxy DHCP non-response

dnsmasq sees PXE requests but never responds. Remove the known-host
filter to determine if tag matching is the issue or if the problem
is elsewhere in the proxy DHCP flow.

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

internal/pxe/supervisor.go

@@ -185,7 +185,6 @@ bind-interfaces
 
 dhcp-range={{.Subnet}},proxy
 dhcp-hostsfile={{.HostsFile}}
-dhcp-ignore=tag:!known
 
 enable-tftp
 tftp-root={{.TFTPRoot}}