[Tobore2000]

AC-026

Summary

• add lender-authorized liquidate(lender, borrower, loan_id) for loans past repayment deadline
• mark written-off loans as LoanStatus::Defaulted and emit a default event
• update lender balance, borrowed principal, active-loan liquidity, and total lender balance consistently
• replace the placeholder default test and update lending documentation

Validation

• git diff --check passed
• cargo test -p acbu_lending_pool test_loan_default_scenario is blocked in the local Windows environment because the MSVC link.exe linker is not installed