feat(deployment)!: move dnsConfig to deployment.dnsConfig

`dnsConfig` was a top-level value although it exclusively configures the pod spec of the Gitea Deployment. With
`affinity` and `env` already moved into the `deployment` dict, keeping `dnsConfig` at the root level leaves the
Deployment configuration split across two places and makes it harder to see which values end up in the rendered
pod spec.

Moving it into the `deployment` dict continues the consolidation of Deployment-scoped values and keeps the
values structure predictable for the remaining pod-level settings.

A deprecation check is added so that existing installations fail fast with an actionable error message. Without
it, a custom DNS configuration would be dropped silently, which typically surfaces much later as unexplained
name resolution failures inside the Gitea pod.

BREAKING CHANGE: `dnsConfig` no longer exists. Use `deployment.dnsConfig` instead. Installations that still set
`dnsConfig` will fail unless `checkDeprecation` is set to `false`.

Co-authored-by: Copilot <copilot@github.com>

templates/gitea/deployment.yaml

@@ -439,9 +439,9 @@ spec:
       tolerations:
         {{- toYaml . | nindent 8 }}
     {{- end }}
-    {{- if .Values.dnsConfig }}
+    {{- if .Values.deployment.dnsConfig }}
       dnsConfig:
-        {{- toYaml .Values.dnsConfig | nindent 8 }}
+        {{- toYaml .Values.deployment.dnsConfig | nindent 8 }}
     {{- end }}
       volumes:
         - name: init