Implement Multi-Signature Monitoring

# 🧠 Concept
Monitor multisig wallet activity.

## ⚠️ Problem
Multisig changes can impact organizational security.

## 📁 Implementation Scope
- src/modules/monitoring/multisig/

## ✅ Requirements
- Signer tracking
- Approval monitoring
- Threshold change detection

## 🎯 Acceptance Criteria
- [ ] Multisig activity tracked
- [ ] Changes detected
- [ ] Alerts generated