fix: simplify EmployeeQuestionnaireNew to use invite-only flow

- Remove all authentication and org context dependencies
- Simplify component to work only with invite codes from URL
- Remove complex user/employee matching logic
- Keep exact Figma UI components and styling
- Use only submitViaInvite function for API submissions
- Employees never need to log in, only use invite link

src/pages/Onboarding.tsx

@@ -3,7 +3,7 @@ import { useNavigate } from 'react-router-dom';
 import { useAuth } from '../contexts/AuthContext';
 import { useOrg } from '../contexts/OrgContext';
 import { onboardingSteps, OnboardingData, initializeOnboardingData } from '../data/onboardingSteps';
-import { secureApiPOST, secureApi } from '../services/secureApi';
+import { secureApi } from '../services/secureApi';
 import {
     FigmaOnboardingIntro,
     FigmaOnboardingQuestion,