feat(sidecar): Add option to adjust the sidecar URL env

[heidyv01]

Problem

The URL environment variable for the node-red-sidecar container was hardcoded to use an internal cluster URL structure (http://..svc.cluster.local:). This prevented users from pointing the sidecare to a different service endpoint which is necessary for e.g. an HA Setup.

Solution

• Modified the deployment.yaml template to make the URL variable configurable.
• Introduced a new url parameter in the values.yaml under .Values.sidecar.env.
• If .Values.sidecar.env.url is not set or left empty, the chart automatically falls back to generating the original dynamic internal cluster URL.

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