chore(repo): prepare v0.1.0-rc.1 launch

[DevChiniwala]

What changed

Prepares the public v0.1.0-rc.1 launch without publishing packages or container images.

• adds focused issue forms, CODEOWNERS, Dependabot, support guidance, and a review checklist
• constrains workflow permissions and pins every GitHub Action by immutable commit
• adds the real-product README demo and the 1280x640 social-preview asset
• records release-candidate notes and updates launch status documentation

Verification

• Python lint and formatting
• Python type checking
• 59 backend and SDK tests
• Web type checking, ESLint, Prettier, and production build
• Live browser capture through Production Health, failure evidence, regression review, and Release Gate
• npm audit: 0 vulnerabilities
• pip-audit: no known vulnerabilities after excluding editable first-party packages
• Gitleaks history and staged-diff scans
• Independent-project naming scan: 0 matches
• Local README links and launch media metadata

Release boundary

This PR does not create a tag or release and does not publish Python or container artifacts. Tagging v0.1.0-rc.1 remains gated on this exact candidate passing quality and hero-e2e and on the final launch review.

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