(SP: 1) [Frontend] Fix guest result screen lost on language switch #261

Goal

Allow guests to change language on quiz result screen without losing their result.

Problem

1. Guest completes quiz → sees result screen
2. Guest clicks language switch (UA → EN)
3. Guest sees Rules screen instead of Result ❌
4. Pending result in localStorage is safe, but UI shows wrong state

Root Cause

Two issues:

Issue A: Session cleared for guests

// QuizContainer.tsx - handleSubmit
clearQuizSession(quizId);  // Ran for ALL users, including guests

Issue B: Only 'in_progress' sessions restored

// quiz-session.ts - loadQuizSession
if (data.status !== 'in_progress') {
  clearQuizSession(quizId);
  return null;
}

Solution

Fix A: Only clear session for authenticated users

// QuizContainer.tsx - handleSubmit
if (!isGuest) {
  clearQuizSession(quizId);
}

Fix B: Allow restoring 'completed' sessions

// quiz-session.ts - loadQuizSession
if (data.status === 'rules') {  // Changed condition
  clearQuizSession(quizId);
  return null;
}
// Now 'completed' sessions are also restored

Files Changed

Testing Checklist

• Guest completes quiz → sees result
• Guest switches language → still sees result
• Guest clicks "Login" → redirects to login
• After login → dashboard shows saved banner
• Authenticated user → session cleared after submit (unchanged)

User Experience

• Guest can now change language on result screen
• Result stays visible, "Login to save" buttons still work
• No data loss — pending result in localStorage preserved