The ornamental design for a cardbox, as shown and described.
FIG. 1 is a perspective view of a card box illustrating my new design;
FIG. 2 is a front view of the card box;
FIG. 3 is a rear view of the card box;
FIG. 4 is a left side view of the card box;
FIG. 5 is a right side view of the card box;
FIG. 6 is a top view of the card box;
FIG. 7 is a bottom view of the card box;
FIG. 8 is an exploded view of the card box of FIG. 1 that shows how a top portion, a middle portion and a bottom portion fit together; and,
FIG. 9 is another exploded view of the card box of FIG. 1 with the middle portion shown in an unfolded condition, with the interior of the middle portion shown face up.
The broken lines in the drawings including the word “Cards” present in FIGS. 1-2 and FIG. 8 depict environmental subject matter only and form no part of the claimed design.