Replace terraform-infra with terraform-netbox

terraform-infra was scoped to NetBox plus Kea DHCP, but Kea is managed by
the kea-operator CRDs in argocd-apps; the two declare the same subnets and
would fight. The repo is narrowed to the NetBox side and renamed to match.

- add the terraform-netbox repository (squash-only, Owners-gated, pre-commit
  and plan required)
- remove terraform-infra

config/git.unkin.net/unkin/repository/terraform-netbox.yaml

@@ -1,7 +1,8 @@
-description: "YAML-driven Terraform for NetBox IPAM, networks, and devices + Kea DHCP"
+description: "YAML-driven Terraform for NetBox: prefixes, IPs, devices, platforms and custom fields"
 private: false
 default_branch: "main"
 default_delete_branch_after_merge: true
+default_merge_style: "squash"
 branch_protection:
   - rule_name: "main"
     merge_whitelist_teams: