Rename terraform-ipam -> terraform-infra

Scope grew beyond IPAM (devices, provisioning). Renaming the config file renames
the managed repo; the gitea provider archives the old terraform-ipam repo
(archive_on_destroy=true) and creates terraform-infra. terraform-ipam only holds an
auto-init README, so nothing is lost.

Claude-Session: https://claude.ai/code/session_01JUoARVdmhxKQHyyyp1pxeT

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

@@ -1,4 +1,4 @@
-description: "YAML-driven Terraform for NetBox IPAM prefixes and Kea DHCP scopes"
+description: "YAML-driven Terraform for NetBox IPAM, networks, and devices + Kea DHCP"
 private: false
 default_branch: "main"
 default_delete_branch_after_merge: true