ci: add CodeQL code scanning

[RobThePCGuy]

Adds GitHub CodeQL static security analysis via a committed Actions workflow (advanced setup). Runs on push/PR to main, a weekly schedule, and manual dispatch. Uses build-mode: none for the javascript-typescript analysis. File-only change; no settings modified.

[gemini-code-assist]

Note

Gemini is unable to generate a review for this pull request due to the file types involved not being currently supported.

[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.