feat: set preferred MFA method from account settings

Adds the ability for users to change their preferred/primary MFA method
when both TOTP and email are available.

Backend:
- Add PUT /auth/mfa/preferred-method endpoint with validation
  (method must be totp/email, MFA must be enabled, TOTP must be
  configured if selecting totp)
- Add totp_configured and email_configured fields to MFA status
  endpoint (totp = has secret + enabled, email = always when enabled)
- Fix setupEmail() to preserve mfa_secret so TOTP config survives
  when email is set up as a second method

Frontend (organizer + portal):
- Add useSetPreferredMethod() composable to useMfa.ts
- Add totp_configured/email_configured to MfaStatus type
- SecurityTab method cards now show "Primaire methode" chip on the
  preferred method and "Als primair instellen" button on the other
- Portal security section shows per-method rows with status chips
  and primary switching

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/Http/Controllers/Api/V1/Auth/MfaSetupController.php

@@ -11,6 +11,7 @@ use App\Enums\MfaMethod;
 use App\Services\MfaService;
 use Illuminate\Http\JsonResponse;
 use Illuminate\Http\Request;
+use Illuminate\Validation\Rule;
 
 final class MfaSetupController extends Controller
 {
@@ -140,9 +141,40 @@ final class MfaSetupController extends Controller
             'confirmed_at' => $user->mfa_confirmed_at?->toIso8601String(),
             'backup_codes_remaining' => $this->mfaService->getRemainingBackupCodeCount($user),
             'is_required' => $this->mfaService->isMfaRequired($user),
+            'totp_configured' => $user->mfa_enabled && $user->mfa_secret !== null,
+            'email_configured' => $user->mfa_enabled,
         ]);
     }
 
+    public function setPreferredMethod(Request $request): JsonResponse
+    {
+        $request->validate([
+            'method' => ['required', Rule::in(['totp', 'email'])],
+        ]);
+
+        $user = $request->user();
+
+        if (! $user->mfa_enabled) {
+            return $this->error('MFA is niet ingeschakeld.', 422);
+        }
+
+        $method = $request->input('method');
+
+        if ($method === 'totp' && $user->mfa_secret === null) {
+            return $this->error('Authenticator app is niet geconfigureerd.', 422);
+        }
+
+        $user->update(['mfa_method' => $method]);
+
+        activity('mfa')
+            ->causedBy($user)
+            ->performedOn($user)
+            ->withProperties(['method' => $method])
+            ->log('mfa.preferred_method.changed');
+
+        return $this->success(['method' => $method], 'Primaire methode gewijzigd.');
+    }
+
     private function verifyBackupCodeForDisable(\App\Models\User $user, string $code): void
     {
         $normalizedCode = strtoupper(str_replace([' ', '-'], '', $code));