Pro-tier honeypots load from an optional decnet/services/pro/ subpackage that
the registry auto-discovers when present; the Community build omits it, so the
directory's absence IS the entitlement gate (no runtime licence check). Recurse
subclasses so a pro service may extend a community one. Exclude pro from the
community wheel and git-ignore the path (it lives in the private
decnet-professional repo).
Add LICENSING.md documenting the dual-license: AGPL-3.0-or-later core plus a
commercial EULA for the Professional tier.
