## Summary
Removes the obsolete Plausible helper script from the hosted auth UI.
## Root cause
The helper endpoint returns 404 on the sign-in page, creating a failed
`script.js` request. The auth UI already uses PostHog, so the unused
Plausible bootstrap can be removed safely.
Fixes#2165.
## Validation
- `pnpm -F @proj-airi/ui-server-auth typecheck`
- `pnpm -F @proj-airi/ui-server-auth lint`
- `pnpm -F @proj-airi/ui-server-auth build`
- `pnpm typecheck`
Deployment is needed to verify the end-to-end hosted sign-in result,
because the local server requires a database configuration that is not
available in this checkout.