Pin puppet master to a single Recreate replica (#341)

## Why

The puppet MASTER is the singleton CA/master. A second master, even transiently during a rolling update, races on CA/cert signing and shared state (the CA lives on a shared PVC mounted by every master pod). The master was previously driven by an HPA with `minReplicas: 2`, `maxReplicas: 5` and a `RollingUpdate` strategy, so 2-5 masters could coexist normally and a rollout would briefly run old+new masters against the same CA data — a latent CA-corruption/split-brain bug. Recreate guarantees the old pod terminates before the new one starts, so two masters never coexist.

## Changes

- Set `puppetserver-master` `spec.replicas: 1` and `spec.strategy.type: Recreate` (drops RollingUpdate).
- Remove the `puppetserver-masters-autoscaler` HPA and its kustomization entry, which forced 2-5 master replicas and would otherwise override `replicas: 1`.
- Refresh the `puppetserver-master-vpa` note to reflect the pinned-singleton, no-HPA state (VPA stays `updateMode: Off`, recommendation-only).

The compiler (`puppetserver-compiler`) remains the horizontally-scalable tier with its own HPA — untouched. puppetdb/puppetboard untouched.

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

Co-authored-by: Ben Vincent <neotheo@gmail.com>
Reviewed-on: #341
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/puppet/deployment_puppetserver-master.yaml

@@ -12,12 +12,13 @@ metadata:
   name: puppetserver-master
   namespace: puppet
 spec:
+  replicas: 1
   selector:
     matchLabels:
       app.kubernetes.io/component: puppetserver
       app.kubernetes.io/name: puppetserver
   strategy:
-    type: RollingUpdate
+    type: Recreate
   template:
     metadata:
       annotations: