Auto-detects the LAN interface from HOST_LAN_IP, sets allow-interfaces in
/etc/avahi/avahi-daemon.conf (idempotent, backs up), restarts avahi. Self-sudos.
Fixes the multi-bridge 'Local name collision' that blocks the mDNS path.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
