lucasAguiar11/mqtt-dotnet — reverse-engineered prompt

Build me a simple C# .NET MQTT demo I can run locally. I want a small solution with a reusable MQTT helper library and two tiny apps, one that publishes messages to a topic and one that subscribes and prints incoming messages to the console. Keep setup easy, with config for broker address, port, topic, client id, and optional username and password.

Please make the subscriber reconnect if the connection drops, and make the publisher easy to test with a sample message or user input. The shared code should live in the library, and the two apps should stay minimal and clear. Add a short README or run notes so I know how to start both apps and see messages flowing.

If anything is unclear, look up current docs online and use sensible defaults.