Add contents:write permission for release job

Fix 403 error when creating GitHub releases. The softprops/action-gh-release
action requires write permission to contents to create tags and releases.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: robinmordasiewicz

.github/workflows/validate-and-release.yml

@@ -242,6 +242,8 @@ jobs:
     needs: [validate, check-release-needed]
     if: needs.check-release-needed.outputs.should_release == 'true'
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
 
     steps:
       - name: Checkout