fix: add HTML marker to PR body so dashboard can detect workflow PRs without label

If --label cve-fixer-automated fails (label doesn't exist in repo),
<!-- cve-fixer-workflow --> in the PR body acts as a reliable fallback.
The dashboard collector checks branch name, title, label, OR body marker.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: vmrh21

workflows/cve-fixer/.claude/commands/cve.fix.md

@@ -1238,6 +1238,7 @@ This PR fixes **CVE-YYYY-XXXXX** by upgrading <package> from X.X.X to Y.Y.Y.
 ---
 
 🤖 Generated by CVE Fixer Workflow
+<!-- cve-fixer-workflow -->
 EOF
 )