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

---------

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

.github/workflows/ci-release-create.yaml

@@ -28,7 +28,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
         with:
           ref: ${{ github.event.inputs.ref }}
 
@@ -47,7 +47,7 @@ jobs:
           printf '%s\n' "$VERSION" > version.txt
 
       - name: Create Pull Request
-        uses: peter-evans/create-pull-request@v6
+        uses: peter-evans/create-pull-request@c5a7806660adbe173f04e3e038b0ccdcd758773c # v6.1.0
         with:
           branch: release/${{ steps.sanitize.outputs.version }}
           commit-message: "chore: release v${{ steps.sanitize.outputs.version }}"