Create project UI styleguide based on CI specifications

The requirement is that the style guide should adhere to the specifications of the Bund ID and the Digitale Dachmarke. On this basis, the following procedure was defined:

• Review of CI specifications: https://nextcloud.fitko.de/apps/files/files/2081651?dir=/Messenger-Kommunikation/UX%26UI/UI%20Design&openfile=true
• Create first draft of styleguide based on decision to CI specifications: https://www.figma.com/design/1p3XZ9tl0awG6w8K7wW5FV/Design-System?m=auto&t=m7h6XQYnSoRo4xmR-6
• Create visual example of a view using several components from the styleguide: https://www.figma.com/design/687cLiqPV6GMTAqjMpBMVL/Views?m=auto&t=m7h6XQYnSoRo4xmR-6

AC

• New: Review by team::dev -> moved to #220 (closed)

Follow-Up

• New: (after style guide is applied to actual screens) Publish styleguide on opencode: https://gitlab.opencode.de/fitko/matrix-g2x/ui-styleguide -> #253

Specification:

• Tool: Figma
• Source: "Erstellung einer Lösungsarchitektur"
• DoD: Design System is validated with FITKO, might change later.
• arc42: linked?