Add workflow_dispatch trigger to CodeQL workflow

Allows manual re-runs from GitHub Actions UI.

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

Author: Chris Shellenbarger

.github/workflows/codeql.yml

@@ -5,6 +5,7 @@ on:
     branches: [master]
   pull_request:
     branches: [master]
+  workflow_dispatch:
   schedule:
     - cron: "0 6 * * 1" # Weekly Monday 6am UTC