SyntaxError: Identifier 'nativeIframe' has already been declared

## Error

```
Identifier 'nativeIframe' has already been declared
```

## Stack trace

```
/users/sign_up:1
```

## Tracking Details
- **Project**: exercism-js
- **Sentry**: [SyntaxError: Identifier 'nativeIframe' has already been declared](https://thalamus-ai.sentry.io/issues/135858286/)
- **Culprit**: ?(users/sign_up)
- **First seen:** Jul 22, 2026

Start with the /users/sign_up entry point and the linked Sentry report; search the website for nativeIframe and inspect where it is declared or included. Reproduce the SyntaxError on the sign-up page and confirm that it loads without duplicate declarations.

Written by the indexing model from the issue text.