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/Quiz.php

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+<?php
+namespace App\Models;
+use Illuminate\Database\Eloquent\Model;
+class Quiz extends Model {
+    protected $fillable = ['subject_id','title','description','active'];
+    protected $casts    = ['active' => 'boolean'];
+    public function subject()   { return $this->belongsTo(Subject::class); }
+    public function questions() { return $this->hasMany(QuizQuestion::class)->orderBy('sort_order'); }
+    public function attempts()  { return $this->hasMany(QuizAttempt::class); }
+}

app/Models/QuizAnswerOption.php

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+<?php
+namespace App\Models;
+use Illuminate\Database\Eloquent\Model;
+class QuizAnswerOption extends Model {
+    public $timestamps = false;
+    protected $fillable = ['quiz_question_id','text','is_correct','sort_order'];
+    public function question() { return $this->belongsTo(QuizQuestion::class,'quiz_question_id'); }
+}

app/Models/QuizAttempt.php

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+<?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 '—';
+    }
+}

app/Models/QuizAttemptAnswer.php

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+<?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'); }
+}

app/Models/QuizQuestion.php

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+<?php
+namespace App\Models;
+use Illuminate\Database\Eloquent\Model;
+class QuizQuestion extends Model {
+    protected $fillable = ['quiz_id','sort_order','type','question_text','time_limit','correct_answer'];
+    public function quiz()          { return $this->belongsTo(Quiz::class); }
+    public function answerOptions() { return $this->hasMany(QuizAnswerOption::class,'quiz_question_id')->orderBy('sort_order'); }
+    public function typeLabel(): string {
+        return match($this->type) {
+            'multiple_choice' => 'Multiple Choice',
+            'exclusion'       => 'Ausschluss',
+            'true_false'      => 'Wahr/Falsch',
+            'free_text'       => 'Freitext',
+            default           => $this->type,
+        };
+    }
+}