Hide the bottom of decks for spectators#1951

Hovering over a face-down card or deck while holding Alt+Shift shows their flipped side. Spectators cannot peek under indivdual cards, which is good and makes sense. If a card is at the bottom of a deck however, spectators can peek at them. It would be nice, if that wasn’t the case.

Alternatively, show grey eyes to signal that a spectator is peeking under a deck.