ci: sync with netresearch/.github templates/go-app (#560)

Auto-opened by sync-template.sh. Brings this repo back into alignment
with the canonical `go-app` template in `netresearch/.github`.

To keep any diverging files, add their paths to
`.github/template.yaml`'s `intentional-drift:` list before merging —
otherwise the next sync run will revert them.

Author: CybotTM

.github/workflows/gitleaks.yml

@@ -14,3 +14,5 @@ jobs:
     permissions:
       contents: read
       security-events: write
+    secrets:
+      GITLEAKS_LICENSE: ${{ secrets.GITLEAKS_LICENSE }}