ci: update action versions to v6 and extend CI to release/hotfix branches (#1955) (#1965)

- Update actions/checkout from v4.2.2 to v6.0.2 in release.yml and
  hotfix.yml (prevents breakage after June 2026 Node.js 20 deprecation)
- Update actions/setup-node from v4.1.0 to v6.3.0 in both workflows
- Add release/** and hotfix/** to test.yml push triggers
- Add release/** and hotfix/** to security-scan.yml PR triggers

test.yml already used v6 pins — this aligns the release pipelines.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/test.yml

@@ -4,6 +4,8 @@ on:
   push:
     branches:
       - main
+      - 'release/**'
+      - 'hotfix/**'
   pull_request:
     branches:
       - main