Fixes ->invoice_number to ->number across all financial listeners, console
commands, and POS services. Fixes ->full_name_ar to ->full_name (participant
accessor) and ->name_ar (person column). Fixes POSService passing wrong keys
('invoice_number' → 'number', 'subtotal' → 'subtotal_amount') to InvoiceService.
Fixes ReceiptService using non-existent participant relationship on Invoice.
Fixes SendOverdueReminders using ->participant instead of ->billable.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>