feat: refactor onboarding into a multi-step flow with dedicated routes and session state management

apps/frontend/src/routes/onboard/verify.tsx

@@ -0,0 +1,6 @@
+import { OnboardVerifyPage } from '@/features/onboard/onboard-verify-page';
+import { createFileRoute } from '@tanstack/react-router';
+
+export const Route = createFileRoute('/onboard/verify')({
+  component: OnboardVerifyPage,
+});