Fix: invoice contact_name uses participant name, not guardian

NewRegistrationWizard was setting contact_name to guardian_name_ar
which made invoices appear under the parent's name instead of the
participant (child). Now uses participant's own person name_ar.

Also fixed 75 existing invoices in production via direct DB update.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Livewire/Receptionist/NewRegistrationWizard.php

@@ -1094,8 +1094,8 @@ public function confirm(): void
                         'type' => 'standard',
                         'billable_type' => Participant::class,
                         'billable_id' => $participant->id,
-                        'contact_name' => $this->guardian_name_ar,
-                        'contact_phone' => $this->guardian_phone,
+                        'contact_name' => $participant->person?->name_ar ?? $this->guardian_name_ar,
+                        'contact_phone' => $participant->person?->phone ?? $this->guardian_phone,
                         'subtotal_amount' => $subtotal,
                         'discount_amount' => $discountAmount,
                         'tax_amount' => 0,