chore: upgrade CodeQL action from v3 to v4

[mcj-coder]

Summary

The CodeQL Action v3 will be deprecated in December 2026. Update all occurrences to v4.

Warning Message

CodeQL Action v3 will be deprecated in December 2026. Please update all occurrences of the CodeQL Action in your workflow files to v4.

Files to Update

• .github/workflows/ci.yml - lines 89, 94

Acceptance Criteria

• github/codeql-action/init@v3 updated to @v4
• github/codeql-action/analyze@v3 updated to @v4
• CI passes with no deprecation warnings