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/QuizAttempt.php

@@ -0,0 +1,20 @@
+<?php
+namespace App\Models;
+use Illuminate\Database\Eloquent\Model;
+class QuizAttempt extends Model {
+    protected $fillable = ['user_id','quiz_id','score','current_question','status','started_at','completed_at'];
+    protected $casts    = ['started_at' => 'datetime', 'completed_at' => 'datetime'];
+    public const POINTS = [1, 1, 2, 2, 3, 3, 4, 6, 8, 10];
+    public function user()    { return $this->belongsTo(User::class); }
+    public function quiz()    { return $this->belongsTo(Quiz::class); }
+    public function answers() { return $this->hasMany(QuizAttemptAnswer::class); }
+    public function stars(): string {
+        $s = $this->score;
+        if ($s >= 40) return '🌟🌟🌟🌟🌟';
+        if ($s >= 30) return '⭐⭐⭐⭐';
+        if ($s >= 20) return '⭐⭐⭐';
+        if ($s >= 10) return '⭐⭐';
+        if ($s >= 1)  return '⭐';
+        return '—';
+    }
+}