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Problem

The accrue_interest() function in contracts/loan_manager/src/lib.rs uses integer division which silently drops fractional interest on every ledger tick. For small loans (e.g. 100 tokens at 12% over 17280 ledgers), the per-ledger interest is less than 1 unit, so every accrual produces 0 and the borrower pays no interest at all. The interest_residual field was added to address this but is not used consistently across all code paths.

Expected Behavior

Fractional interest should accumulate in a residual field and be applied when it crosses a whole unit. All code paths that trigger interest accrual (repay, approve, refinance) should flush the residual.

Suggested Fix

1. Confirm interest_residual is flushed before all repayment and refinance paths
2. Add a test with a loan of 50 tokens that accrues over 100 ledgers and assert interest > 0
3. Add a test that verifies interest_residual resets to 0 after full repayment

Location

contracts/loan_manager/src/lib.rs inside accrue_interest()