feat(app): buffer onboarding answers before auth, flush to profile after sign-up/login

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/auth/login.tsx

@@ -20,6 +20,7 @@ import { AuthService } from '../../services/authService';
 import * as AppleAuthentication from 'expo-apple-authentication';
 import Constants from 'expo-constants';
 import { useSafeAnalytics } from '../../services/analytics';
+import { PreAuthOnboardingService } from '../../services/preAuthOnboardingService';
 
 const ONBOARDING_AUTH_BACKGROUND = {
   light: '#fbfaf3',
@@ -70,6 +71,9 @@ export default function LoginScreen() {
     try {
       const session = await AuthService.login(email, password);
       const billing = await hydrateSession(session);
+      if (session?.userId) {
+        await PreAuthOnboardingService.flushToProfile(session.userId).catch(() => {});
+      }
       const isPro = billing?.entitlement?.plan === 'pro' && billing?.entitlement?.status === 'active';
       // Non-pro accounts land on the paywall with context instead of being
       // bounced through the root redirect (which looks like an app restart).
@@ -118,6 +122,9 @@ export default function LoginScreen() {
         name: fullName || undefined,
       });
       const billing = await hydrateSession(session);
+      if (session?.userId) {
+        await PreAuthOnboardingService.flushToProfile(session.userId).catch(() => {});
+      }
       if (session.isNewUser) {
         await AsyncStorage.setItem('greenlens_show_tour', 'true');
       }