simple reusable components for the frontend

[w-richter]

Add LoadingSpinner, EmptyState, ErrorBoundary components, sonner toast system, App.tsx wrapper, barrel export, and 404 page via root route notFoundComponent

basicly all the stuff you only see when its slow or broken :)

[alexander-wudy]

Is there a way we can check in on the page right now? Like some showcase page? 😅
Because otherwise I think its hard to test if you say it only shows when the page is slow or had errors

[w-richter]

Is there a way we can check in on the page right now? Like some showcase page? 😅 Because otherwise I think its hard to test if you say it only shows when the page is slow or had errors

added a demo page my bad

[alexander-wudy]

Just checked, looks really nice! lgtm ^^