Problem

UDP transport needs a sample application demonstrating end-to-end usage.

Sub-tasks

• Create sample/Magma.Udp.EchoServer - simple UDP echo over the Magma stack
• Or sample/Magma.Udp.DnsForwarder - more compelling demo, forwards DNS queries
• README explaining how to run it, what it demonstrates

Dependencies

Depends on: #108
Unlocks: demonstrates the stack end-to-end for UDP users

Phase

Phase 2 (Platform Backends & Samples)