Set payment limit for Savings -> Loans transfers

It turns out that transfer limits from Savings -> Loans (ie. paying off a loan) are not currently handled by Fineract. Instead, an overpayment mechanism exists, where overpayments can be credited back to a savings account manually.

However, this takes time and backoffice approval.

We could handle overpayment validation in the BFF or frontend layers by validating the loan amount first. Reducing the load on backoffice staff to approve loan overpayments.

No files or tests are named. Start by tracing the Savings → Loans transfer flow and how the loan amount is obtained, then determine whether validation belongs in the BFF or frontend. Done means an overpayment is rejected before the transfer and the behavior is covered by tests.

Written by the indexing model from the issue text.