feat(onboarding): add /welcome route

app/(welcome)/welcome/page.tsx

@@ -0,0 +1,15 @@
+import { redirect } from "next/navigation";
+import { currentUser } from "@/lib/auth/current-user";
+import { isOnboardingDone } from "@/features/onboarding/onboarding-cookie";
+import { OnboardingClient } from "./onboarding-client";
+
+export default async function WelcomePage() {
+    if (await isOnboardingDone()) {
+        redirect("/dashboard/home");
+    }
+
+    const user = await currentUser();
+    const initialStepId = user ? "org-create" : "sso-gate";
+
+    return <OnboardingClient initialStepId={initialStepId} />;
+}