CollectPaymentWizard and ReconciliationWizard were creating payments
without payer_type/payer_id, making them invisible on participant
profiles. Now PaymentService inherits payer from the invoice's
billable when callers omit it. Also auto-generates reference if empty.

Fixed 113 orphaned payments in production.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>