feat: MFA frontend with auth page restyling, challenge screen, and setup wizard

- Restyle organizer auth pages: Dutch text, remove placeholder social login
- Restyle portal auth pages to Vuexy v1 centered card pattern with decorative shapes
- MFA challenge card component with VOtpInput, method tabs, backup code input,
  trusted device checkbox, and session countdown timer
- Login pages handle mfa_required response with device fingerprint header
- Security settings page with TOTP setup (QR code), email setup, disable MFA,
  backup codes regeneration, and trusted devices management
- Portal profile page includes MFA security section
- Admin user detail page shows MFA status with reset button
- MFA enforcement route guard redirects to security settings when required
- Device fingerprint utility for trusted device identification
- MFA types, composables with TanStack Query for both apps

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

api/app/Http/Resources/Admin/AdminUserResource.php

@@ -24,6 +24,7 @@ final class AdminUserResource extends JsonResource
             'created_at' => $this->created_at->toIso8601String(),
             'roles' => $this->getRoleNames()->values()->all(),
             'is_super_admin' => $this->hasRole('super_admin'),
+            'mfa_enabled' => (bool) $this->mfa_enabled,
             'organisations' => $this->whenLoaded('organisations', fn () =>
                 $this->organisations->map(fn ($org) => [
                     'id' => $org->id,