[rewrite] Added shadcn ui to frontend and slightly tweaked backend

frontend/src/routes/(auth)/500.tsx

@@ -0,0 +1,6 @@
+import { createFileRoute } from '@tanstack/react-router'
+import GeneralError from '@/features/errors/general-error'
+
+export const Route = createFileRoute('/(auth)/500')({
+  component: GeneralError,
+})