Superset Helm Chart: configOverrides applied during install causes authentication failures (401 / anonymous user)

### Bug description

## Bug Description

When deploying Apache Superset using the official Helm chart, authentication breaks when configuration is provided via `configOverrides` helm value.

Without `configOverrides`, everything works correctly.

Adding `configOverrides` provided in this report, authentication fails and APIs behave as if the user is anonymous.

Issue starts in Superset **6.1.0**. Superset **6.0.0 works fine**.

---

## To Reproduce

### Working deployment

Install Superset with default Helm values (no `configOverrides`).

Result:
- `/api/v1/security/login` returns valid JWT
- `/api/v1/me/` returns authenticated user
- dashboards load correctly

---

### Broken deployment

Add this to `values.yaml`:

```python
configOverrides:
superset: |
RATELIMIT_STORAGE_URI = CACHE_REDIS_URL

FEATURE_FLAGS = {
"EMBEDDED_SUPERSET": True,
"DASHBOARD_RBAC": True,
}

GUEST_ROLE_NAME = env("SUPERSET_GUEST_ROLE_NAME", "EmbeddedAnalyzer")
GUEST_TOKEN_JWT_SECRET = env("GUEST_TOKEN_JWT_SECRET")
PUBLIC_ROLE_LIKE = "Public"

X_FRAME_OPTIONS = "NONE"

TALISMAN_CONFIG = {
"force_https": True,
"force_https_permanent": True,
"frame_options": None,
"content_security_policy": {
"frame-ancestors": ["'self'", "https://*.mydomain.com"],
},
}

ENABLE_PROXY_FIX = True
```

Deploy:

```bash
helm upgrade --install superset apache/superset -f values.yaml
```

---

## Observed behavior

- `/api/v1/security/login` succeeds
- JWT token is issued
- `/api/v1/me/` returns:

```json
{
"result": {
"is_active": false,
"is_anonymous": true
}
}
```

OR returns `401 Unauthorized`

- dashboards return empty results

---

## Expected behavior

Same config should work whether:

- applied via Helm `configOverrides`, OR
- added manually to `superset_config.py` secret after deployment

---

## Important finding

If I:

1. Deploy without `configOverrides`
2. Manually patch `superset-config` secret and add the config at the end of `superset_config.py` data
3. Restart pods

➡️ Everything works fine

---

## Environment

- Superset: 6.1.0
- Helm chart: official Superset chart
- Kubernetes: DOKS

---

## Notes

This started in Superset 6.1.0.
Same setup works in 6.0.0.

### Screenshots/recordings

_No response_

### Superset version

master / latest-dev

### Python version

3.9

### Node version

16

### Browser

Chrome

### Additional context

_No response_

### Checklist

- [ ] I have searched Superset docs and Slack and didn't find a solution to my problem.
- [ ] I have searched the GitHub issue tracker and didn't find a similar bug report.
- [ ] I have checked Superset's logs for errors and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

Compare the Helm configOverrides deployment with the manually patched superset_config.py in the superset-config secret, using the supplied values.yaml and Superset 6.0.0/6.1.0 behavior as references. Reproduce with helm upgrade --install, then check /api/v1/security/login and /api/v1/me/. Done means configOverrides preserves authenticated users and dashboard access without manual secret changes.

Written by the indexing model from the issue text.