solitaire: detect a won board and finish it in one press

A drained, all-face-up board is a guaranteed clear that auto() sweeps home
in a single cascade, but the only way to trigger it was double-clicking
thirty cards home by hand. Add State.Won(), surface it in the view, and
swap the ordinary controls for one pulsing finish button when it's true.

internal/web/games_solitaire.go

@@ -60,6 +60,7 @@ type solitaireView struct {
 	Passes  int  `json:"passes"` // through the stock, counting this one; -1 unlimited
 	Moves   int  `json:"moves"`
 	CanAuto bool `json:"can_auto"`
+	Won     bool `json:"won"` // every card face up, stock and waste empty: one press finishes it
 
 	Home      int     `json:"home"`       // cards on the foundations
 	PerCard   float64 `json:"per_card"`   // what one more is worth
@@ -86,6 +87,7 @@ func viewSolitaire(g klondike.State) solitaireView {
 		Passes:    g.PassesLeft(),
 		Moves:     g.Moves,
 		CanAuto:   g.CanAuto(),
+		Won:       g.Won(),
 		Home:      g.Home(),
 		PerCard:   g.PerCard(),
 		BreakEven: g.Tier.BreakEven(),