Fix invoice creation: type must be 'standard' not 'enrollment' (CHECK constraint)

invoices.type only allows: standard, recurring, credit_note, proforma.
The wizard was passing 'enrollment' which violated the DB constraint,
causing a silent failure caught by the try/catch.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Livewire/Receptionist/NewRegistrationWizard.php

@@ -311,7 +311,7 @@ public function confirm(): void
                     $invoice = $invoiceService->create([
                         'academy_id' => app('current_academy')->id,
                         'number' => $invoiceService->generateNumber(app('current_academy')->id),
-                        'type' => 'enrollment',
+                        'type' => 'standard',
                         'billable_type' => Participant::class,
                         'billable_id' => $participant->id,
                         'contact_name' => $this->guardian_name_ar,