Matrix-Synapse chart: security hardening, naming scheme, configurable probes

- Values-driven securityContext for the Synapse pod/container with hardened
  defaults: runAsNonRoot as uid/gid 1000 (matching the image's previous gosu
  drop target), readOnlyRootFilesystem, allowPrivilegeEscalation false, all
  capabilities dropped; /tmp mounted as emptyDir. The now-ineffective UID/GID
  env vars are removed (the securityContext controls the user).
- Naming scheme: delegation Deployment renamed to ...-delegation-nginx-deployment,
  ConfigMap to ...-delegation-nginx-configmap (references and service selector
  updated).
- matrix.configSecretRef moved to secrets.configSecretRef (repo standard).
- Probes for Synapse and the delegation nginx are values-configurable;
  defaults are the previous hardcoded settings.
- Flexible ingress standard: ingress.className (default nginx) and
  ingress.annotations merged with the cert-manager annotation.
- Additive matrix.env block rendered through tpl (value/secretKeyRef/
  configMapKeyRef forms).
- CI fixtures: secret ref moved, seed job image synced to appVersion.
- Chart 4.2.1+upv1.159.0 -> 5.0.0+upv1.159.0 (major; app version unchanged).

matrix-synapse/templates/matrix-delegation-nginx.configmap.yaml

@@ -2,7 +2,7 @@
 apiVersion: v1
 kind: ConfigMap
 metadata:
-  name: {{ .Release.Name }}-{{ .Chart.Name }}-delegation-nginx-config
+  name: {{ .Release.Name }}-{{ .Chart.Name }}-delegation-nginx-configmap
 data:
   nginx.conf: |
     worker_processes 1;