security: harden CI against supply-chain attacks (#20476)

- Pin all third-party actions to SHA
- Gate claude.yml triggers to internal authors with Harden-Runner egress
audit
- Ignore fork-PR lifecycle scripts
- Narrow cross-repo dispatch payloads
- Add 7d npm release-age gate
- Add CODEOWNERS on .github/** and .yarnrc.yml

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Co-authored-by: prastoin <paul@twenty.com>

.github/actions/restore-cache/action.yaml

@@ -25,7 +25,7 @@ runs:
       run: |
         echo "CACHE_PRIMARY_KEY_PREFIX=v4-${CACHE_KEY}-${REF_NAME}" >> "${GITHUB_OUTPUT}"
     - name: Restore cache
-      uses: actions/cache/restore@v4
+      uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0 (restore)
       id: restore-cache
       with:
         key: ${{ steps.cache-primary-key-builder.outputs.CACHE_PRIMARY_KEY_PREFIX }}-${{ github.sha }}