A module cannot know the private network's CIDR — it is a per-mesh value chosen
at genesis — but sometimes must name it: an intrusion filter that must never
ban a tunnel peer. Carry the overlay range on the Rendering and offer it as the
machine fact mesh-range, the same way a machine's own address is offered, so the
module names it rather than hardcoding a value (data is the mesh's). Absent when
the mesh has no range. Enables the fail2ban ignoreip fix.
jschoubben