- Firmware: add VERSION? command returning BUILD_NR for version check
- Android: flash button checks firmware version first, skips flash if current
- After flash: auto key exchange via reboot detection (expectingReboot flag)
- device_filter.xml + intent-filter: USB permission 'always allow' checkbox
- singleTop + onNewIntent prevents unwanted SettingsActivity launch on USB connect
- platformio.ini: upload_port updated to /dev/ttyACM1