Feature/loan manager view accrual issue 7

[Francis6-git]

Description:
This PR resolves Issue #7, fixing a discrepancy where the get_loan view function was evaluating interest and late fee accruals on a localized copy of the Loan struct without updating persistent storage. This caused returned states to diverge from subsequent state-changing contract entries.

Closes #7

[ogazboiz]

clean addition. the read-only quote_total_debt view delegates to the same current_total_debt helper that repay uses, so the quote always matches what actually gets charged, and the test proves it by asserting balance_before minus balance_after equals the quoted debt and the loan ends Repaid. no state mutation beyond the ttl bump (which the rest of the file does too), accrual is by elapsed ledgers not call count, and it returns LoanNotFound on a missing loan rather than panicking. ci is green. merging.

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