Fix onboarding process not getting the subcription plan

frontend/src/components/domain/onboarding/OnboardingWizard.tsx

@@ -104,10 +104,14 @@ export const OnboardingWizard: React.FC = () => {
         console.log('🔄 Auto-completing user_registered step for new user...');
         setAutoCompletionAttempted(true);
 
+        // Merge with any existing data (e.g., subscription_plan from registration)
+        const existingData = userRegisteredStep?.data || {};
+
         markStepCompleted.mutate({
           userId: user.id,
           stepName: 'user_registered',
           data: {
+            ...existingData, // Preserve existing data like subscription_plan
             auto_completed: true,
             completed_at: new Date().toISOString(),
             source: 'onboarding_wizard_auto_completion'