Add Quiz feature: 10-question quizzes with progressive scoring (max 40 pts)

- Quizzes table with questions, answer options, attempts, answers
- Question types: multiple_choice, exclusion, true_false, free_text
- Progressive scoring: [1,1,2,2,3,3,4,6,8,10] = max 40 per quiz
- Alpine.js countdown timer per question with auto-submit on timeout
- Admin: CRUD for quizzes + per-question editor, JSON export/import
- Child: quiz overview with best scores, question view, result breakdown
- Nav: Quiz link in child header and admin sidebar

app/Models/QuizAttemptAnswer.php

@@ -0,0 +1,8 @@
+<?php
+namespace App\Models;
+use Illuminate\Database\Eloquent\Model;
+class QuizAttemptAnswer extends Model {
+    protected $fillable = ['quiz_attempt_id','quiz_question_id','answer_given','is_correct','points_earned'];
+    public function attempt()  { return $this->belongsTo(QuizAttempt::class,'quiz_attempt_id'); }
+    public function question() { return $this->belongsTo(QuizQuestion::class,'quiz_question_id'); }
+}