Chore(dns): align resolver diagnostics with runtime usage

Keep resolver health checks on demand and surface actionable runtime availability failures through the shared logger. Remove the GitHub Actions workflow so transient resolver connectivity does not affect code CI.

Co-authored-by: OpenAI Codex <codex@openai.com>

package.json

@@ -18,6 +18,7 @@
     "start-frontend": "node frontend-server.js",
     "start": "concurrently \"node frontend-server.js\" \"node --import ./sentry-instrument.js backend-server.js\"",
     "purge-index": "node scripts/purge-index-cache.js",
+    "dns-check": "node scripts/check-dns-resolvers.js",
     "fetch-favicons": "node scripts/fetch-favicons.js",
     "i18n-status": "node scripts/i18n-status.js",
     "i18n-new": "node scripts/i18n-scaffold.js new",