Migration applied to prod: approved/paid public.bills mirror into
accounting.bills (Payables) with find-or-create vendor + line item
(external_source='acmacc_bill'/'acmacc_vendor'). When an accounting bill is
marked paid (paid_amount>=total), the linked public.bills is set status=paid
(+paid_date, amount_paid) and its bill_approvals marked paid. Loop-guarded
with is-distinct-from. Backfilled 370 bills/45 vendors; totals reconcile.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
