ci: sync with netresearch/.github templates/go-app (#547)

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/check-template-drift.yml

@@ -5,6 +5,7 @@ on:
     branches: [main]
   push:
     branches: [main]
+  merge_group:
 
 permissions: {}