ci: publish npm package with provenance

[ConnectFontes]

Summary

Updates the npm publish workflow to publish the package with provenance, as required by the n8n Creator Portal.

Changes

• Configures actions/setup-node with the npm registry URL.
• Passes NODE_AUTH_TOKEN from the NPM_TOKEN GitHub Actions secret.
• Forces npm provenance with NPM_CONFIG_PROVENANCE=true.

Context

The package n8n-nodes-rdsc@0.0.1 was published successfully, but the n8n Creator Portal blocked the submission because that version was not published with provenance.

After this workflow change is merged, we need to publish a new version, e.g. 0.0.2, because npm versions are immutable and 0.0.1 cannot be republished.

Validation

• Existing package metadata was checked locally.
• npm pack --dry-run --json succeeds.
• The previous GitHub Actions run passed lint, build, and package generation; the remaining issue is the provenance requirement for npm publish.