Handle both paho-mqtt v1.x and v2.x in MQTTPublisher:
- Try v2.x format with callback_api_version first
- Fall back to v1.x format if needed
- Ensures compatibility across different paho-mqtt versions
Fixes: ValueError when using paho-mqtt 2.0+
Created SETUP_ON_PI.md with comprehensive instructions for:
- Pulling latest changes on the Pi
- Installing system dependencies (Bluetooth, Python)
- Setting up virtual environment
- Configuring Bluetooth permissions
- Setting up configuration files
- Running test
- Troubleshooting common issues
- Environment variable reference
Enables seamless development workflow between machines.
