Userinterface customization no longer applies

### Describe the bug

I have had customizations set for ages via atrributes of a group according to Documentation:
https://docs.goauthentik.io/customize/interfaces/user/#enablingdisabling-features

```
settings:
theme:
background: >
background: url('https://picsum.photos/1920/1080'); filter: blur(8px);
background-position: center; background-repeat: no-repeat;
background-size: cover;
enabledFeatures:
search: false
settings: true
apiDrawer: false
applicationEdit: false
notificationDrawer: true
```

These settings no longer apply to members of the group, Background does not apply. Search ApiDrawer and applicationEdit is not disabled. This applies to Superusers and normal users. I have also put these settings into the branding attributes section and the users attributes section which did not work either.

### How to reproduce

1. Apply theme settings or enabledFeatures via Groups Membership or Branding
2. log into user interface as Superuser or non Superuser from a private browser window

### Expected behavior

Settings apply as documented.

### Screenshots

Settings:

Unprivileged user:

Superuser:

### Additional context

_No response_

### Deployment Method

Kubernetes

### Version

2025.12.1

### Relevant log output

```shell

```

Start by reproducing the documented theme and enabledFeatures settings through group membership, branding, and user attributes, using the customization documentation linked in the report. Compare the resulting interface for superusers and unprivileged users with the configured values; done means the background and feature visibility settings apply as documented.

Written by the indexing model from the issue text.