Switch to bluetoothctl-only approach.
- rfkill approach caused bluetoothd to mark hci1 as 'off-blocked'
- Now uses bluetoothctl to select hci0 → power off, select hci1 → power on
- hci0 stays Powered: no (invisible to GUI), hci1 stays Powered: on (fully functional)
- Script waits for bluetoothd before issuing commands