403 : Forbidden XSRF cookie does not match POST argument

### Bug description

Hi! I have successfully set up the JupyterHub on top of kubernetes. However, when I enable Native Authentication, and try to sign up as a new user, I get the error: `403 : Forbidden XSRF cookie does not match POST argument`.

I also reported the same issue here: https://github.com/jupyterhub/nativeauthenticator/issues/289

### How to reproduce

There is the basic configuration of hub using Helm `config.yaml` file:

```yaml
hub:
config:
JupyterHub:
authenticator_class: native
NativeAuthenticator:
open_signup: true
```

### My personal set up

* [Helm chart version](https://hub.jupyter.org/helm-chart/): `4.3.11`
* JupyterHub is served over HTTPS
* Ingress is set-up by cloud provider, not by `config.yaml` file

Here are some relevant logs:

Logs

```

[I 2025-11-22 13:55:38.478 JupyterHub _xsrf_utils:130] Setting new xsrf cookie for b'None:=' {'path': '/hub/', 'max_age': 3600}

[I 2025-11-22 13:55:38.494 JupyterHub log:192] 200 GET /hub/signup (@::ffff:) 16.94ms

[I 2025-11-22 13:55:54.403 JupyterHub _xsrf_utils:130] Setting new xsrf cookie for b'' {'path': '/hub/', 'max_age': 3600}

[W 2025-11-22 13:55:54.403 JupyterHub web:1932] 403 POST /hub/signup (::ffff:): XSRF cookie does not match POST argument

[W 2025-11-22 13:55:54.436 JupyterHub log:192] 403 POST /hub/signup (@::ffff:) 33.57ms

```

I cannot figure out any more relevant information. I tried to migrate to other Helm Chart versions, setting `JuputerHub: trusted_downstream_ips: []` and some configuration with `JupyterHub: tornado_settings:` in `config.yaml` file and deleting browser cookies, but nothing worked. Weirdly enough, Dummy Authentication and Google Authetnication work just fine.

Thanks for help in advance!!!