[Bug](components): The time adjustement buttons of the DateTimePicker are invisible

**Description**

In Storybook and in Supernova Scheduled Silences you can adjust the time. There are also buttons - needed are not - but they seem to be invisible / wrong styled.

<img width="377" height="221" alt="Image" src="https://github.com/user-attachments/assets/a53f87a7-6e63-4b9f-ba0c-8e37f86916ab" />
