REDESIGN: Unify usage of Colors

[Marcel-TO]

Description

In the current project, each page uses hardcoded often different colors for background and text. This causes issues when trying to maintain the style and design. Especially since the project supports darkmode and lightmode

Especially if one wants to adjust the color values for the whole project.

Solution

Use the already implemented tailwind variables for background and foreground variables. This ensures easy maintainability and usability through every theme