Assess late fees (finance charges)

Triggers finance charge assessment for the entity. By default assesses all overdue invoices for all active customer accounts. Pass account_id to scope to a single customer. Pass dry_run: true to preview which invoices would receive a charge and the calculated amounts without persisting any records.

Assessment logic: For each overdue invoice the handler checks eligibility (account not late-fee-exempt, invoice status open/partially_paid, balance_due meets the entity minimum, grace period elapsed, no same-day duplicate). The fee is calculated per the entity compounding mode (monthly, daily, or none). A new late_fee_invoice document is created and a GL journal entry is posted (DR accounts_receivable 1300 / CR finance_charge_income 4220) per ASC 310-10-35.

Entity settings required: late_fee_enabled must be true and late_fee_rate_percent must be a non-null positive number in the entity settings before any charges are assessed.

Idempotency: At most one late-fee invoice is issued per source invoice per day. Repeated calls on the same day return skipped results for already-charged invoices.