Reset button behavior

[abrondijk]

By holding down the button during power on, the device should erase its settings (NVS partition), for a full factory reset.

During normal operation, this button should function as a "fallback" button, to navigate through the UI. It should have the same functionality as the strain sensor based button, with the addition of a reset timer. If the fallback button is pressed down for longer than X (TBD) seconds, it should also factory reset itself.