Redesign(front theme) 🎨🎉 & tweaks (routing, etc.)

* Complete redesign of the frontend theme => mobile friendly++ 🎨🎉
* Redesigned how the theme can be customized
* (adapted the backend to store the theme correctly + testing)
* Added a default theme for the app
* Centralized routing in the APP for consistency
* Quick fix to prevent rerendering on layout change in the university page

(backend migration required)

Fixes #19 #20
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