[surveyform] saveResponse Issue: Not authenticated

⚠️IMPORTANT: please make sure to remove any private data from the “Submitted Data” log⚠️

### Submitted Data:

```
{
"td2026__user_info__japan_province__choices": "ibaraki",
"td2026__user_info__years_in_japan__choices": "range_over_20",
"td2026__user_info__residency_status__choices": "permanent_resident",
"td2026__user_info__country": "BRA",
"td2026__user_info__age__choices": "range_50_59",
"td2026__user_info__years_of_experience__choices": "range_over_20",
"td2026__user_info__professional_qualifications__choices": [
"short_cycle"
],
"td2026__user_info__language_proficiency_english__choices": "fluent",
"td2026__user_info__language_proficiency_japanese__choices": "business",
"td2026__user_info__jlpt_level__choices": "none",
"td2026__user_info__other_japanese_certifications__choices": [
"na"
],
"td2026__user_info__gender__choices": "man",
"td2026__user_info__identify_as_lgbtq__choices": "no",
"td2026__user_info__religion__choices": "religious",
"lastSavedAt": "2026-09-01T12:06:06.651Z",
"locale": "en-US"
}
```

### Location

https://surveys.tokyodev.com/en-US/survey/tokyodev/2026/iy5-1U0YcELrA7kH6p03K/1

### Timestamp

Tue Sep 01 2026 21:06:06 GMT+0900 (Japan Standard Time)

### Error:

```
{
"id": "not_authenticated",
"status": 401,
"message": "Not authenticated"
}
```

Reproduce the failure at the supplied survey URL and trace the saveResponse request that returns the not_authenticated 401 response. Check the authentication path for saving survey responses, while keeping submitted data private; done means an authenticated respondent can save a response without this error.

Written by the indexing model from the issue text.