Convert BTDemo to Maven and add CI verification

[google-labs-jules]

Converted the BTDemo project from the legacy Ant structure to the new Maven project structure. This includes:

1. Generating a new Maven project using the cn1app-archetype.
2. Porting the source code and resources.
3. Updating the source code to remove the dependency on ca.weblite.codename1.json and use standard java.util.Map and com.codename1.io.JSONParser (implied via library callbacks) instead, as the library now uses Maps for callbacks.
4. Configuring the Maven project to depend on the cn1-bluetooth-lib snapshot.
5. Adding a step to the GitHub Actions workflow to verify that the BTDemo project builds successfully against the library snapshot.

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PR created automatically by Jules for task 3924683271490555664 started by @shai-almog

[google-labs-jules]

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