fix(web): avoid hard reload during host restart

[papi-ux]

Summary

• Return a clean restart response before Polaris terminates/restarts.
• Add a shared Web UI restart helper that waits for Polaris to come back instead of force-reloading into a dead HTTPS listener.
• Use the helper from both Config Apply and Troubleshooting Restart, with EN/ZH status messages.

Notes

Refs #114.

This targets the Apply/Restart race path. The reporter also mentioned the TLS page can appear while idle/login, so this may be a partial mitigation rather than the whole root cause.

Validation

• git diff --check
• npm test — 16 files / 66 tests
• npm run lint
• npm run build