Fix rollback safeguards and chaos payment testing

[gotethry]

Summary

• add automatic rollback safeguards to detect stale incomplete transfer flows and trigger escrow refunds safely
• emit rollback and reconciliation lifecycle events so incomplete-flow remediation is observable
• add end-to-end chaos testing support for payment flows, including injected API downtime, blockchain latency, and recovery-rate validation

Verification

• tests were intentionally not run per request; changes were implemented with targeted unit-test coverage updates in transfer lifecycle and stress modules

Closes #198
Closes #199

Made with Cursor