Add ESP32 ultrasonic WebSocket example with Python control server

[musfaagv]

Motivation

• Provide a complete example showing ESP32 ↔ Python WebSocket communication for ultrasonic telemetry and remote LED control.
• Make it easy to test sending distance in cm and inch from an ESP32 and receiving server-initiated LED on/off commands.

Description

• Add example_firmware/websocket_ultrasonic/server.py, an asyncio WebSocket server that accepts JSON sensor telemetry, prints cm/inch values, and broadcasts LED commands via an interactive terminal (on/off/list/help/exit).
• Add example_firmware/websocket_ultrasonic/websocket_ultrasonic.ino, an ESP32 sketch that reads an HC-SR04, converts to cm and inch, sends JSON telemetry to the server, and applies received LED commands.
• Extend example_firmware/README.md with protocol examples, wiring notes (HC-SR04 ECHO voltage warning), and instructions to run the server (python server.py) and upload the sketch.

Testing

• Ran python3 -m py_compile example_firmware/websocket_ultrasonic/server.py, which completed successfully.
• Performed repository validation steps and created the change commit (files added: server.py, websocket_ultrasonic.ino, and README updates).

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Codex Task