Add API Versioning Support

# 🧠 Concept
Support future API evolution.

## ⚠️ Problem
Breaking changes become difficult without versioning.

## 📁 Implementation Scope
- src/api/

## ✅ Requirements
- Versioned routes
- Documentation updates
- Backward compatibility strategy

## 🎯 Acceptance Criteria
- [ ] API versioning enabled
- [ ] Routes documented
- [ ] Future versions supported