fix(ospo): rename national-digital-twin to national-node-net

[syed-awsaf-informed]

Alignment of GitHub actions to the new organisation (National-Digital-Twin -> National-Node-Net), plus dependent secret renames and CHANGELOG entry.

[github-actions]

✅ OSS Checks Passed

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📊 Total Files	🟢 Passed	🔴 Failed	🧮 Score
13	13	0	100%

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[Copilot]

Pull request overview

This PR updates repository documentation and GitHub Actions workflow configuration to reflect the organisation rename from National-Digital-Twin to National-Node-Net, ensuring links and cross-repo workflow access target the correct org.

Changes:

• Updated README links to point to National-Node-Net/archetypes.
• Updated oss-checker workflow to request GitHub App tokens and check out source repositories from National-Node-Net.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
README.md	Updates the archetypes contributing link to the renamed organisation.
profile/README.md	Updates the archetypes contributing link to the renamed organisation.
.github/workflows/oss-checker.yml	Updates org/repo references used for GitHub App token scoping and checkouts.

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[cruddasj]

@syed-awsaf-informed - as this is a special org level repository for documentation purposes, only the README.md file needs updated. It should be exempt from normal checks and rulesets.