fix(clickhouse): honour cluster mode off when using cloud

[pjhampton]

If you try to use ClickHouse Cloud, you cannot currently set clickhouse.clusterEnabled: false because of this block. You should be able to set it regardless.

{{- if and .Values.clickhouse.deploy ($.Values.clickhouse.replicaCount | int | eq 1) }}
- name: CLICKHOUSE_CLUSTER_ENABLED
  value: "false"
{{- end }}

The workaround is:

langfuse:
  additionalEnv:
    - name: CLICKHOUSE_CLUSTER_ENABLED
      value: "false"

and this PR updates the chart.

IMPORTANT: unit test vibe coded. Please review.

---

Important

Updates Helm chart to allow disabling ClickHouse cluster mode in cloud environments and adds tests for this behavior.

• Behavior:
  • Updates condition in _helpers.tpl to set CLICKHOUSE_CLUSTER_ENABLED to false when clickhouse.deploy is false or clickhouse.replicaCount is 1.
  • Ensures CLICKHOUSE_CLUSTER_ENABLED is not set for multi-replica deployments.
• Tests:
  • Adds clickhouse-cluster_test.yaml to verify CLICKHOUSE_CLUSTER_ENABLED is false for external ClickHouse and single replica deployments.
  • Verifies CLICKHOUSE_CLUSTER_ENABLED is not set for multi-replica deployments.

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[CLAassistant]

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[Steffen911]

@pjhampton Thank you a lot for raising this. I've implemented another approach via #255 where we evaluate the clusterEnabled flag of the values.yaml to make the decision.

I agree that the opt-out using the additional env is unintuitive, but I'd like to keep the default behaviour that assumes an external ClickHouse is clustered.

With the alternative in place, I'll close this PR.