Introduce a level selection UI and persistence for unlocked levels. Adds CSS styles and HTML markup for a floating level menu, and JS to load/save highest unlocked level to localStorage (key: mirror-game-highest-unlocked-level). Implements functions to render/toggle the menu, unlock levels on finish, and navigate to arbitrary levels via goToLevel. nextLevel now delegates to goToLevel, and setup calls loadUnlockedLevels() and setupLevelMenu() so the menu reflects progress immediately.
Adjust UI visuals: change page background to #FFF6E5, increase main container border-radius from 10px to 150px, and soften toolbox corners (5px → 15px). Add a new .game-title CSS rule (responsive font-size, weight, color, letter-spacing, centered) and insert an <h1 class="game-title">Mirror Game</h1> into the game template. These are visual polish changes only; no gameplay logic was modified.
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.
