Adds base__mesh_coordinator_pin (default empty = no-op). When set + base__mesh_enabled,
a lineinfile task writes "<ip> <fqdn>" to /etc/hosts so a managed mesh host survives a
local-DNS hiccup (the 2026-06-18 incident class). FQDN derived from base__mesh_management_url
via regex_replace (no community.general). Gated on base__mesh_enabled | bool and pin length;
the coordinator host (askari/offsite_hosts) stays exempt. Production pin wired for ubongo
(77.42.120.136). Molecule dns_servers fix included (Docker/NetBird DNS incompatibility).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
