feat(deploy): k8s manifests for microk8s (vncmail.sandbox.vnc.de)

Bulwark is stateful (local /app/data) — Vercel serverless (read-only fs)
crashes it. Deploy as a container with 4 persistent volumes on microk8s,
alongside bulwark.sandbox.vnc.de. Adds deploy/k8s/ (namespace, pvc, deployment,
service, ingress, secret template, runbook) + rewrites setup doc off Vercel.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

deploy/k8s/service.yaml

@@ -0,0 +1,14 @@
+apiVersion: v1
+kind: Service
+metadata:
+  name: vncmail-plus
+  namespace: vncmail
+  labels:
+    app: vncmail-plus
+spec:
+  selector:
+    app: vncmail-plus
+  ports:
+    - name: http
+      port: 80
+      targetPort: 3000