0820: Improve UI and fix BLE communication issues

- Remove unnecessary Master/Scan buttons, keep only Start/Advertise
- Fix -2500 timeout error by pausing scan before advertising
- Optimize RecyclerView updates to fix click event issues during scanning
- Add comprehensive error code handling for all AT API errors
- Add automatic scan resume after successful advertising
- Add toolbar with settings menu for beacon configuration

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Co-Authored-By: Claude <noreply@anthropic.com>