When ip_range changes in Settings, the new subnet is now applied to:
- DNS zone records (network_manager.apply_ip_range)
- Caddy virtual IPs (firewall_manager.ensure_caddy_virtual_ips)
- iptables per-service rules (firewall_manager.update_service_ips)
- docker-compose.yml static IPs if writable (ip_utils.update_docker_compose_ips)
New module ip_utils.py derives all container IPs from the subnet using
fixed offsets so the entire stack stays consistent from one setting.
321 tests pass (72 new tests added for ip_utils, apply_ip_range, update_service_ips).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
