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-utils.yaml

@@ -25,7 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event.action != 'closed'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
       - name: Install dependencies
         uses: ./.github/actions/yarn-install
       - name: Utils / Run Danger.js
@@ -38,7 +38,7 @@ jobs:
     runs-on: ubuntu-latest
     if: github.event.action == 'closed' && github.event.pull_request.merged == true
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4.3.1
       - name: Install dependencies
         uses: ./.github/actions/yarn-install
       - name: Run congratulate-dangerfile.js