ci: enable release freeze during preparation

.github/workflows/prepare-release.yml

@@ -25,6 +25,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     permissions:
+      actions: write
       contents: write
       pull-requests: write
     steps:
@@ -33,6 +34,12 @@ jobs:
       with:
         egress-policy: audit
 
+    - name: Enable release freeze
+      env:
+        GH_TOKEN: ${{ github.token }}
+      run: |
+        gh variable set RELEASE_FREEZE --body true --repo "${GITHUB_REPOSITORY}"
+
     - name: Checkout repository
       uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
       with: