nix-cache02: add homelab-deploy builder service

- Configure builder to build nixos-servers and nixos (gunter) repos
- Add builder NKey to Vault secrets
- Update NATS permissions for builder, test-deployer, and admin-deployer
- Grant nix-cache02 access to shared homelab-deploy secrets

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

flake.lock

@@ -28,11 +28,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1770648258,
-        "narHash": "sha256-sExxD8N9Q0RrHIoppOV6qp4jcJirLVjpQd20C72V78I=",
+        "lastModified": 1770758165,
+        "narHash": "sha256-jjCcxhZavm2r7gjZ2+FNOMvTYQsRlIa9ijPICK0HVk4=",
         "ref": "master",
-        "rev": "277a49a666347e2e2ae67128cf732956a9c3be56",
-        "revCount": 27,
+        "rev": "a8aab16d0e7400aaa00500d08c12734da3b638e0",
+        "revCount": 32,
         "type": "git",
         "url": "https://git.t-juice.club/torjus/homelab-deploy"
       },