Build subscription fraud detection with real-time monitoring

## Context
Payments need fraud detection.

## Current Limitation
No fraud detection exists.

## Expected Outcome
- Real-time fraud detection
- Fraud risk scoring
- Fraud alerts
- Fraud analytics

## Acceptance Criteria
- [ ] Real-time fraud detection
- [ ] Fraud risk scoring
- [ ] Fraud alert system
- [ ] Fraud analytics
- [ ] Fraud investigation
- [ ] Fraud reporting
- [ ] Fraud documentation