Improve logic around the header in the search nav

What does this MR do and why?

We simply can choose not to provide the header from the backend and set it ourselves in the Frontend.

Fixes the search sidebar in vite as well.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. use vite
2. go to the global search page