Retrieves the outstanding balance for an application as of a given date, including remaining principal, scheduled interest, fines, and late charges. Useful for settlement calculations and payment planning.

Accrual rules applied to overdue installments:

• Fine (multa): 2% of the overdue installment amount, applied once per overdue installment.
• Late interest (juros de mora): 1% per month (proportional daily) on the overdue installment amount × days overdue.
• remaining_interest reflects only scheduled interest on future (non-overdue) installments.
• outstanding_balance = remaining_principal + remaining_interest + fine_amount + late_interest.
• early_settlement_amount = outstanding_balance × 0.95 (5% discount for early settlement).
• For REFUNDED, CANCELLED, and APPLICATION_DECLINED applications, returns HTTP 200 with all balance fields set to 0.0 and the application status in the response body. No outstanding debt in any of these states.