feat: add configurable speed and expanded grid presets for snake

- Add per-game speed setting with presets (Slow/Normal/Fast/Insane)
- Add speed selector UI in snake lobby
- Expand grid presets with Tiny (15x15) and XL (50x30)
- Auto-calculate cell size based on grid dimensions
- Preserve speed setting in rematch games

ui/lobby.go

@@ -21,6 +21,8 @@ type LobbyProps struct {
 	SnakeSoloClicks     []h.H
 	SnakeMultiClicks    []h.H
 	ActiveSnakeGames    []*snake.SnakeGame
+	SelectedSpeedIndex  int
+	SpeedSelectClicks   []h.H
 }
 
 func LobbyView(p LobbyProps) h.H {
@@ -41,7 +43,7 @@ func LobbyView(p LobbyProps) h.H {
 
 	var tabContent h.H
 	if p.ActiveTab == "snake" {
-		tabContent = SnakeLobbyTab(p.SnakeNicknameBind, p.SnakeSoloClicks, p.SnakeMultiClicks, p.ActiveSnakeGames)
+		tabContent = SnakeLobbyTab(p.SnakeNicknameBind, p.SnakeSoloClicks, p.SnakeMultiClicks, p.ActiveSnakeGames, p.SelectedSpeedIndex, p.SpeedSelectClicks)
 	} else {
 		tabContent = connect4LobbyContent(p)
 	}