fix: add missing sanctum auth guard config and register driver

The main branch was using auth:sanctum middleware on routes but
config/auth.php had no sanctum guard defined. This caused:

  Auth guard [sanctum] is not defined.

Fix:
1. Add the sanctum guard entry to config/auth.php with
   driver=sanctum and provider=users
2. Register the sanctum guard driver in AppServiceProvider::boot()
   as a safety net via Auth::resolved()

app/Providers/AppServiceProvider.php

@@ -9,6 +9,7 @@ use App\Services\Attendance\StudentAttendanceWriterService;
 use App\Services\Attendance\TeacherAttendanceSubmissionService;
 use Illuminate\Foundation\Http\FormRequest;
 use Illuminate\Routing\Redirector;
+use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\ServiceProvider;
 
 class AppServiceProvider extends ServiceProvider
@@ -24,6 +25,25 @@ class AppServiceProvider extends ServiceProvider
 
     public function boot(): void
     {
+        // Ensure the sanctum guard driver is always registered
+        Auth::resolved(function ($auth): void {
+            $auth->extend('sanctum', function ($app, $name, array $config) use ($auth) {
+                return tap(
+                    new \Illuminate\Auth\RequestGuard(
+                        new \Laravel\Sanctum\Guard(
+                            $auth,
+                            config('sanctum.expiration'),
+                            $config['provider'] ?? null,
+                            config('sanctum.last_used_at', true),
+                        ),
+                        request(),
+                        $auth->createUserProvider($config['provider'] ?? null),
+                    ),
+                    fn ($guard) => app()->refresh('request', $guard, 'setRequest'),
+                );
+            });
+        });
+
         $this->app->resolving(FormRequest::class, function (FormRequest $request, $app): void {
             $request->setContainer($app)->setRedirector($app->make(Redirector::class));
         });

config/auth.php

@@ -44,6 +44,10 @@ return [
             'driver' => 'jwt',
             'provider' => 'users',
         ],
+        'sanctum' => [
+            'driver' => 'sanctum',
+            'provider' => 'users',
+        ],
     ],
 
     /*