feat: Fund flow audit — fix all critical/high/medium gaps (Go/Rust/Python/TS)

[devin-ai-integration]

Summary

Comprehensive fund flow audit across 485+ routers identified 15 gaps where money moves without proper accounting, events, or idempotency. All fixed across TypeScript, Go, Rust, and Python.

CRITICAL fixes (9 production-blocking issues)

Race condition — cashIn/cashOut balance read was OUTSIDE the transaction. Now uses SELECT ... FROM agents WHERE id = $1 FOR UPDATE inside withTransaction() to prevent concurrent overdraw.

Missing GL journal entries — 6 routers moved money without double-entry:

• chargebackManagement: GL reversal on refund (Debit 5001 Chargeback Expense → Credit 1001 Cash)
• disputeRefund: GL reversal on refund (Debit 5002 Refund Expense → Credit 1001 Cash)
• reversalApproval/transactionReversalManager: GL reversal + balance restoration on approve
• ecommerceOrders: GL reversal on refund/cancel status
• crossBorderRemittance.send: Was only creating audit log — now debits float, creates GL entries (Debit 3001 Remittance Payable → Credit 2001 Agent Float), checks CBN limits, publishes Kafka events

Wrong table query — multiCurrencyExchange.convert was querying agentPushSubscriptions instead of doing FX conversion. Completely rewritten with 15 currencies (NGN/USD/EUR/GBP/GHS/XOF/KES/ZAR/EGP/USDT/USDC/TZS/UGX/RWF/ZMW), 48 bidirectional corridors, FOR UPDATE locking, GL double-entry, and Kafka events.

BNPL repayment — bnplEngine had zero repayment flow. Added processRepayment mutation (FOR UPDATE → debit float → GL entry → late penalty calculation → Kafka event) and collectOverdue batch processor.

HIGH fixes

• airtimeVending, billPayments, splitPayments: Added publishEvent() Kafka domain events
• floatTopUp, merchantPayments, recurringPayments: Added idempotencyKey input + withIdempotency() wrapping + Kafka events

MEDIUM fixes

• savingsProducts: Added calculateInterest (compound interest with daily/monthly/quarterly/annual compounding) and accrueInterest mutation with GL entries. Replaced hardcoded stub responses with real DB queries.

Polyglot microservices

Service	Language	Port	Capabilities
fund-flow-engine	Go	8250	BNPL repayment (serializable tx), FX conversion (GL + spread), reversal execution, GL reconciliation
fund-flow-settlement	Rust	8251	BNPL installment scheduling (amortization), FX rate engine (16 corridors, spread calc), reconciliation
fund-flow-analytics	Python	8252	BNPL portfolio analytics, credit risk scoring (0-1000), FX forecasting (SMA/EMA), reversal fraud detection, anomaly detection (z-score)

Test impact

• 0 new TypeScript errors (6 pre-existing: react-i18next/@dnd-kit type declarations)
• 4,241 tests pass, 5 fail (4 pre-existing db-performance/critical-flows, 1 expected: sprint46 multi-currency test expects activePairs: 42 from old hardcoded stub — now dynamically computed as 48 due to expanded corridor coverage)
• Go: go vet passes
• Python: py_compile passes

Link to Devin session: https://app.devin.ai/sessions/3ebd42bf0430422a9a2bd85ed9f9cd4c
Requested by: @munisp

[devin-ai-integration]

Original prompt from Patrick

https://drive.google.com/file/d/1ko3y7OBp1tJIXGTbe2QGFRHMQfxMTWHX/view?usp=sharing

1. Extract ALL everything in the archive
2. how do ensure and assess that features for example domain and business logic/rules/requirements are fully impemented and production ready and complete - can you thoroughly assess each files and features to determine there are ready for production

1. Database integration (replace in-memory with real Postgres)
2. Inter-service HTTP wiring with retries/circuit breakers
3. Security hardening (JWT everywhere, remove hardcoded creds, mTLS)
4. Integration tests for critical flows
5. Graceful shutdown, observability, alerting
   3)search for orphan, partially and generic scaffolded features across the platform - fully implement them end to end -generic CRUD-only patterns , modules with no domain logic, disconnected features, and incomplete implementations.

[devin-ai-integration]

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