Teardown freed the view port before unhooking the serial and status
callbacks, which run on the BLE/BT thread and call view_port_update. A late
notification or status change during exit could touch freed memory. Unhook
both callbacks and restore the default profile first, then free the view port.
Brings up the Flipper as a connectable serial GATT peripheral via the bt service profile API and echoes what a central writes. Restores the default profile on exit.
andy