KIT navigation and overview per domain

### Description

**As** Domain focuses stakholder,
**I want** to quickly find all KITs related to my domain ,
**so that** can decide quickly what to put my focus on for the data ecosystem adoption.

### Acceptance Criteria

- [ ] Domain filter created at least with one domain
- [ ] Header navigation includes the relevant domain seperators
- [ ] Sidebar view includes the relevant seperators

### Additional Information

- disussed in KIT office hour at 27.08.2026 with @matbmoser for feasiblity
- first KITs to implement are the Engineering related KITs
- Filter is based on https://eclipse-tractusx.github.io/Kits/cross-industry
- domains are already set in kitsData.js

Development branch: https://github.com/manourym/CX-KIT-development/tree/domain-categories