Detect Missing Replay Protection

# 🧠 Concept  
Detect transactions lacking replay protection.

## ⚠️ Problem  
Replay attacks may duplicate transactions.

## 📁 Implementation Scope  
- `rules/security/signatures/`

## ✅ Requirements  
- Detect missing nonces/domain separators  
- Warn developers  

## 🎯 Acceptance Criteria  
- [ ] Replay risks detected  