fix: quiet federated media status probes

[atomantic]

Summary

• Treat periodic federated media status discovery failures as quiet control-plane responses.
• Authenticate and resolve peers before disclosing provider state, while naming the peer locally when real work is rejected.
• Separate local diagnostics from federation response text and add regression coverage.

Test plan

• cd server && npm test -- --run lib/errorHandler.test.js services/federatedMediaProvider.test.js services/federatedMediaConsumer.test.js services/instances.test.js routes/federatedMedia.test.js ../scripts/generate-api-route-catalog.test.js
• cd server && npm test -- --exclude ../scripts/checkNpmVersion.test.js --silent=passed-only --reporter=default (35,418 passed; the omitted environment guard requires the repository npm 12 toolchain while this host currently provides npm 11)