Add GitHub CodeQL scanning workflow

[Copilot]

Adds CodeQL static analysis scanning to the repository for the C/C++ codebase.

Changes

• New workflow .github/workflows/codeql.yml:
  • Triggers on push/PR to master and weekly schedule (Mondays 03:20 UTC)
  • Runs on ubuntu-22.04 with required CodeQL permissions
  • Installs the same build dependencies as the existing CI (libcunit1-dev liblua5.3-dev lcov)
  • Performs an explicit make build before analysis (required for compiled languages)
  • Uses github/codeql-action v3 with c-cpp language matrix

[github-advanced-security]

You are seeing this message because GitHub Code Scanning has recently been set up for this repository, or this pull request contains the workflow file for the Code Scanning tool.

What Enabling Code Scanning Means:

• The 'Security' tab will display more code scanning analysis results (e.g., for the default branch).
• Depending on your configuration and choice of analysis tool, future pull requests will be annotated with code scanning analysis results.
• You will be able to see the analysis results for the pull request's branch on this overview once the scans have completed and the checks have passed.

For more information about GitHub Code Scanning, check out the documentation.