Fix: type confliction if using WiFi and ETH

[hideakitai]

Related:

• Choosing between WiFi and Ethernet during runtime #128

[Copilot]

Pull Request Overview

Introduces a wrapper UDP type (ETHUdp) to eliminate template/type conflicts when using both WiFi and Ethernet ArtNet managers concurrently, and adds a combined send/receive example for WiFi + Ethernet.

• Defines ETHUdp (deriving from WiFiUDP) and updates template specializations and aliases to use it.
• Adds a new example demonstrating simultaneous WiFi and Ethernet ArtNet send/receive.

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
ArtnetETH.h	Adds ETHUdp type and updates specializations/aliases to avoid WiFi/Ethernet UDP type conflicts.
examples/Multiple/send_receive_eth/send_receive_eth.ino	New example showing concurrent WiFi and Ethernet ArtNet usage.

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