Stack cards on home screen and make them scrollable

[haardikk21]

PREREQ: Reusable card component
NOTE: Cards scroll left-right not up-down as in the image

Since the user can have multiple credentials, potentially hundreds, we want to show them in the app without having a super long list so that the "History" part is still visible.

As in the image, the cards on the homescreen should be stacked and scrollable in place. Look into Flutter's "Stack" component for this.