feat: Implement Phase 3 REST API server with comprehensive endpoints

Implements comprehensive REST API for Cloud Safeguard with:
- Run management endpoints (create, update, delete, status, cancel)
- Agent management endpoints (list, get, run, status)
- Policy management endpoints (list, get, evaluate)
- System endpoints (health, status, metrics, events)
- Event streaming integration with WebSocket support
- Standardized API response format with error handling

Files added:
- internal/web/api.go - Complete REST API handlers
- internal/web/events.go - Event streaming infrastructure
- examples/k8s-test/deployment.yaml - Sample K8s manifest

Files modified:
- internal/web/server.go - Integrated EventStream and API routes
- cmd/simctl/main.go - Added Kubernetes support and watch command
- internal/orchestrator/engine.go - Added Kubernetes adapter integration

Phase 3 Progress: REST API Server ✅ Complete
Next: API Authentication, OpenAPI Spec, Security Agents