Add comprehensive zone management for DNS master functionality:
- vortexctl zone list/dump/import/export/reload commands
- Secondary DNS provider configuration (OVH support)
- RPCD methods for LuCI integration
- ACL permissions for new methods
This enables importing zones from external providers (Gandi) and
configuring OVH as secondary DNS with SecuBox as authoritative master.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>