Rewrites the PXE section of the ops runbook around the new proxy-DHCP
model (no dedicated bridge, coexists with UniFi/pfSense/etc.) and
swaps the e2e test's default bridge + orchestrator URL to match. The
e2e file now calls out the LAN-DHCP precondition in its header so
future-me (or CI) doesn't hang at PXE wondering why nothing answers.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>