Dual-write ENC data into encapi alongside Cobbler

Seed encapi (statuses, roles, prodnxsr node assignments) and make the
instance module also create an encapi_node for every VM, so the k8s
puppetserver ENC can cut over from Cobbler. Cobbler/puppetca/puppetdb
resources are left untouched.

- Add config/encapi leaf + modules/encapi driving statuses/roles/nodes
  from YAML (3 statuses, 51 roles, 13 prodnxsr physical nodes).
- Add encapi_node to modules/instance (certname, role, environment).
- Wire encapi provider into root.hcl required_providers and the module
  providers; plumb ENCAPI_WRITE_TOKEN via Makefile vault_env.

config/encapi/nodes.yaml

@@ -0,0 +1,44 @@
+# encapi node assignments for the 13 prodnxsr* physical nodes.
+# These hosts are NOT managed by the incus instance module (they are the
+# bare-metal hypervisors / k8s nodes), so they are seeded here explicitly.
+# certname -> role from the PuppetDB enc_role fact; environment=develop to
+# match their current catalog_environment.
+prodnxsr0001.main.unkin.net:
+  role: roles::infra::k8s::control
+  environment: develop
+prodnxsr0002.main.unkin.net:
+  role: roles::infra::k8s::control
+  environment: develop
+prodnxsr0003.main.unkin.net:
+  role: roles::infra::k8s::control
+  environment: develop
+prodnxsr0004.main.unkin.net:
+  role: roles::infra::k8s::compute
+  environment: develop
+prodnxsr0005.main.unkin.net:
+  role: roles::infra::k8s::compute
+  environment: develop
+prodnxsr0006.main.unkin.net:
+  role: roles::infra::k8s::compute
+  environment: develop
+prodnxsr0007.main.unkin.net:
+  role: roles::infra::k8s::compute
+  environment: develop
+prodnxsr0008.main.unkin.net:
+  role: roles::infra::k8s::compute
+  environment: develop
+prodnxsr0009.main.unkin.net:
+  role: roles::infra::incus::node
+  environment: develop
+prodnxsr0010.main.unkin.net:
+  role: roles::infra::incus::node
+  environment: develop
+prodnxsr0011.main.unkin.net:
+  role: roles::infra::incus::node
+  environment: develop
+prodnxsr0012.main.unkin.net:
+  role: roles::infra::incus::node
+  environment: develop
+prodnxsr0013.main.unkin.net:
+  role: roles::infra::incus::node
+  environment: develop