Digiweb's BRAS answers PADI only on a single-tagged ISP VLAN (pon-isp,
10); the double-stacked wan-pon (131) transport never got a PADO because
the UniFi access switch can't push the outer tag onto already-tagged
ingress frames (no QinQ/tag-stacking). Attach VLAN 10 directly to the
physical `lan` link for now.
Kept reversible via a `wanStacked` flag: flip it back to true to restore
the 131->10 stack once a QinQ-capable device sits in front of the ONT.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>