Add per-cell laserSegments tracking and use it to render correct laser orientation: introduce laserSegments global, reset it at trace start, populate entries when tracing, and consult it in loadGrid to choose horizontal vs vertical classes. Update UI styling from a dark to a lighter theme (body and main backgrounds, cell/empty/mirror/wall colors and laser gradients), remove some borders/fit-content sizing, and add a "map" class to the map container in the HTML. These changes fix laser orientation rendering and refresh the game's visual theme.
