feat(onboarding): add cookie helper, types and mock data

src/features/onboarding/onboarding-cookie.ts

@@ -0,0 +1,17 @@
+'use server';
+
+import { cookies } from 'next/headers';
+
+const COOKIE_NAME = 'portabase_onboarding';
+const DONE_VALUE = 'done';
+
+export async function isOnboardingDone() {
+    return (await cookies()).get(COOKIE_NAME)?.value === DONE_VALUE;
+}
+
+export async function markOnboardingDone() {
+    (await cookies()).set(COOKIE_NAME, DONE_VALUE, {
+        path: '/',
+        maxAge: 60 * 60 * 24 * 365,
+    });
+}