fix(submodules): update cyberchef-mcp with .gitmodules configuration

Updates cyberchef-mcp submodule to commit 9df7416c which adds the missing
.gitmodules file for the ref-proj/CyberChef submodule.

This resolves Git exit code 128 warnings in all GitHub Actions workflows:
- Warning: 'The process '/usr/bin/git' failed with exit code 128'
- Error: 'fatal: No url found for submodule path components/cyberchef-mcp/ref-proj/CyberChef in .gitmodules'

The warnings appeared during the Post Run actions/checkout@v6 cleanup phase
when git attempted to recursively process submodules. With the .gitmodules
file now present, git can properly handle the nested CyberChef submodule.

Affected workflows: CI, GUI CI, Release
All warnings eliminated while maintaining zero functional impact.

Author: doublegate