Add grade/Klasse system: assign class levels to users, questions, and quizzes

- users.grade: set per child in admin (Klasse 1–10)
- quizzes.grade, questions.grade: optional target class (null = all)
- Children only see content matching their grade or without grade set
- Admin views show grade badge in user list, quiz list, questions list
- Quiz create/edit and user create/edit have Klasse dropdown

app/Http/Controllers/Admin/QuizController.php

@@ -18,8 +18,8 @@ class QuizController extends Controller {
     }
 
     public function store(Request $r) {
-        $r->validate(['title'=>'required|string|max:120','subject_id'=>'required|exists:subjects,id','description'=>'nullable|string|max:500']);
-        $quiz = Quiz::create($r->only('title','subject_id','description') + ['active'=>true]);
+        $r->validate(['title'=>'required|string|max:120','subject_id'=>'required|exists:subjects,id','description'=>'nullable|string|max:500','grade'=>'nullable|integer|min:1|max:13']);
+        $quiz = Quiz::create($r->only('title','subject_id','description') + ['active'=>true,'grade'=>$r->grade ?: null]);
         return redirect()->route('admin.quizzes.edit', $quiz)->with('success','Quiz erstellt – jetzt Fragen hinzufügen.');
     }
 
@@ -30,8 +30,8 @@ class QuizController extends Controller {
     }
 
     public function update(Request $r, Quiz $quiz) {
-        $r->validate(['title'=>'required|string|max:120','subject_id'=>'required|exists:subjects,id','description'=>'nullable|string|max:500']);
-        $quiz->update($r->only('title','subject_id','description') + ['active'=>$r->boolean('active')]);
+        $r->validate(['title'=>'required|string|max:120','subject_id'=>'required|exists:subjects,id','description'=>'nullable|string|max:500','grade'=>'nullable|integer|min:1|max:13']);
+        $quiz->update($r->only('title','subject_id','description') + ['active'=>$r->boolean('active'),'grade'=>$r->grade ?: null]);
         return back()->with('success','Quiz gespeichert.');
     }
 

app/Http/Controllers/Admin/UserController.php

@@ -15,6 +15,7 @@ class UserController extends Controller {
             'name'     => 'required|string|max:60',
             'email'    => 'required|email|unique:users',
             'password' => 'required|min:6',
+            'grade'    => 'nullable|integer|min:1|max:13',
         ]);
         User::create([
             'name'     => $r->name,
@@ -22,6 +23,7 @@ class UserController extends Controller {
             'password' => Hash::make($r->password),
             'role'     => 'child',
             'points'   => 0,
+            'grade'    => $r->grade ?: null,
         ]);
         return redirect()->route('admin.users.index')->with('success','Kind-Konto erstellt.');
     }
@@ -32,8 +34,9 @@ class UserController extends Controller {
             'email'    => 'required|email|unique:users,email,'.$user->id,
             'password' => 'nullable|min:6',
             'points'   => 'required|integer|min:0',
+            'grade'    => 'nullable|integer|min:1|max:13',
         ]);
-        $user->fill(['name'=>$r->name,'email'=>$r->email,'points'=>$r->points]);
+        $user->fill(['name'=>$r->name,'email'=>$r->email,'points'=>$r->points,'grade'=>$r->grade ?: null]);
         if ($r->filled('password')) $user->password = Hash::make($r->password);
         $user->save();
         return redirect()->route('admin.users.index')->with('success','Gespeichert.');

app/Http/Controllers/Child/LearnController.php

@@ -22,14 +22,24 @@ class LearnController extends Controller {
         $answeredToday = QuestionAttempt::where('user_id',$user->id)
             ->whereDate('created_at', today())
             ->pluck('question_id');
+        $grade    = $user->grade;
         $question = $subject->activeQuestions()
             ->whereNotIn('id', $answeredToday)
+            ->where(function($q) use ($grade) {
+                $q->whereNull('grade');
+                if ($grade) $q->orWhere('grade', $grade);
+            })
             ->with('answerOptions')
             ->inRandomOrder()
             ->first();
         // Falls alle beantwortet: ganz random
         if (!$question) {
-            $question = $subject->activeQuestions()->with('answerOptions')->inRandomOrder()->first();
+            $question = $subject->activeQuestions()
+                ->where(function($q) use ($grade) {
+                    $q->whereNull('grade');
+                    if ($grade) $q->orWhere('grade', $grade);
+                })
+                ->with('answerOptions')->inRandomOrder()->first();
         }
         if (!$question) {
             return redirect()->route('learn.subjects')->with('info','Noch keine Fragen für dieses Fach.');

app/Http/Controllers/Child/QuizController.php

@@ -8,7 +8,12 @@ class QuizController extends Controller {
 
     public function index() {
         $subjects = Subject::all()->keyBy('id');
+        $grade    = auth()->user()->grade;
         $quizzes  = Quiz::with('subject')->where('active',true)
+            ->where(function($q) use ($grade) {
+                $q->whereNull('grade');
+                if ($grade) $q->orWhere('grade', $grade);
+            })
             ->withCount('questions')->get()->groupBy('subject_id');
         $bestScores = QuizAttempt::where('user_id',auth()->id())
             ->where('status','completed')

app/Models/User.php

@@ -5,7 +5,7 @@ use Illuminate\Foundation\Auth\User as Authenticatable;
 use Illuminate\Notifications\Notifiable;
 class User extends Authenticatable {
     use HasFactory, Notifiable;
-    protected $fillable = ['name','email','password','role','points'];
+    protected $fillable = ['name','email','password','role','points','grade'];
     protected $hidden = ['password','remember_token'];
     protected $casts = ['email_verified_at' => 'datetime', 'password' => 'hashed'];