matrix-synapse: restart the delegation nginx when its ConfigMap changes

The delegation nginx serves the .well-known documents from an nginx.conf that
is rendered from ingress.domain and mounted with subPath. Changing the domain
rewrote the ConfigMap but left the running pod untouched: the pod template was
unchanged, so nothing rolled, and the kubelet never refreshes a subPath mount.
The pod kept serving the old delegation while looking perfectly healthy - the
failure mode from #82.

The pod template now carries checksum/config over the rendered delegation
ConfigMap, so a changed nginx.conf rolls the deployment.

Also documents the limit that remains for homeserver.yaml: it comes from a
1Password-backed Secret, whose content Helm never sees, and the operator's own
auto-restart only ever covers Deployments - not this StatefulSet. That case
needs a manual rollout restart, which the values.yaml now says out loud.

Major bump: runtime behavior changes - a delegation config change now costs a
restart of the nginx pod (a few seconds, no persistent state).

matrix-synapse/Chart.yaml

@@ -3,7 +3,7 @@ name: matrix-synapse
 description: A Helm chart to deploy a Matrix Synapse server on Kubernetes
 icon: https://raw.githubusercontent.com/element-hq/synapse/develop/docs/favicon.png
 type: application
-version: 5.0.0+upv1.159.0
+version: 6.0.0+upv1.159.0
 appVersion: "v1.159.0"
 maintainers:
   - name: jklein