Improve OpenSSF Scorecard score

[silvanocerza]

This PR makes the following changes in an effort to enhance the OpenSSF Scorecard score:

• Call MCP Registry publish from the PyPI workflow
• Set read-only top-level workflow permissions
• Add Dependabot for uv, Actions and Docker
• Add a security policy
• Pinned actions, images and release tooling
• Add CodeQL analysis
• Add build provenance on releases

[linear-code]

ENG-879

[github-advanced-security]

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