Add terragrunt-enc repository

terragrunt-enc will be the single source of truth for encapi ENC data
(statuses, roles, node classifications), managed via Terraform/Terragrunt,
superseding Cobbler classification for Puppet.

- Add config/git.unkin.net/unkin/repository/terragrunt-enc.yaml (public,
  default_branch main, delete-branch-after-merge, squash merges).
- Protect main: block direct pushes, require the two Woodpecker PR status
  checks (pre-commit, plan), and whitelist benvin for approvals.

config/git.unkin.net/unkin/repository/terragrunt-enc.yaml

@@ -0,0 +1,13 @@
+description: "Single source of truth for encapi ENC data (statuses, roles, nodes), managed via Terraform/Terragrunt. Supersedes Cobbler node classification for Puppet."
+private: false
+default_branch: "main"
+default_delete_branch_after_merge: true
+default_merge_style: "squash"
+branch_protection:
+  - rule_name: "main"
+    enable_push: false
+    status_check_contexts:
+      - "ci/woodpecker/pr/pre-commit"
+      - "ci/woodpecker/pr/plan"
+    approval_whitelist_users:
+      - "benvin"