fix(cron): prevent duplicate repayment_due notifications per loan

[MarvyNwaokobia]

Summary

• Add Redis-based dedup guard (24h TTL per loan) so loanCheckCron sends at most one repayment_due notification per loan per 24-hour window, stopping the spam of 24+ notifications/day
• Replace the hardcoded 30 days heuristic with the actual due date computed from term_ledgers * LEDGER_CLOSE_SECONDS, matching how loanController calculates next_payment_deadline
• Distributed lock was already in place (kept as-is)

Changes

• src/cron/loanCheckCron.ts — Rewrote the SQL to use term_ledgers for due date calculation; added cacheService.setNotExists per-loan dedup before creating notifications
• src/tests/loanCheckCron.test.ts — New test file with 4 test cases: lock skip, single notification, dedup skip, and mixed multi-loan scenario

Test plan

• All 4 cron tests pass (npm test -- --testPathPattern=loanCheckCron)
• TypeScript compiles without errors
• Verify with a seeded DB that only one notification is created per due loan across multiple cron runs

Closes #10

[ogazboiz]

this is solid, the dedup is done right: a real redis lock (cacheService.setNotExists(loan_due_notified:${loanId}, "1", 24h) in src/cron/loanCheckCron.ts:57-66), so the first caller per loan in the 24h window sends and the rest continue, no in-memory set that resets. the query correctly targets contract_events (not the loan_events view) with valid columns, and mock ordering/completeness are fine. one thing blocks it:

1. prettier fails on src/tests/loanCheckCron.test.ts (lines ~31, 66, 101, 135-137), and CI's lint step fails the whole job on that. run: npx prettier --write src/tests/loanCheckCron.test.ts

minor, not blocking: if setNotExists marks the key but createNotification then throws, the catch aborts and the key stays set for 24h, suppressing that loan's notification even though nothing was sent. consider deleting the key on send failure (or notify-then-mark) so a transient error doesn't swallow the notification.

heads up: your CI run is gated (first PR, action_required), i'll approve it so you get the signal. fix the prettier line and this is ready.

if you want to keep contributing, join us on Telegram: https://t.me/+DOylgFv1jyJlNzM0

[ogazboiz]

the prettier item is fixed and the dedup logic is solid (real redis lock loan_due_notified:, query targets contract_events not the loan_events view). you also picked up my non-blocking note, there's now a test for releasing the dedup key when the notification send fails so it can retry. merging once ci is green. nice.

if you want to keep contributing, join us on Telegram: https://t.me/+DOylgFv1jyJlNzM0

ps: CI is red right now on the migrate step, but that is a pre-existing main-branch issue (a commonjs migration file under our ESM package), nothing to do with your change. once that is sorted this lands.