Add OnlineMode route and extract app styles

Introduce an OnlineMode route and placeholder component, wire it into the router and Home menu (replace the removed local-vs-bot entry). Rename utils/index.ts to router/index.ts and add the new /onlineMode route; update main.ts to import the router from ./router and include the new app.css. Extract shared #game and .game-content styles into GUI/src/app.css and remove the duplicate styles from LocalMode.vue. Make small UI tweaks: adjust GameEndedMenu width, minor formatting/attribute fixes in Layout.vue and LocalMode.vue.

GUI/src/Home.vue

@@ -6,15 +6,11 @@ let buttons = [
         color: "red",
         componentName: "LocalMode"
     },
-    {
-        name: "Lokal gegen Bot",
-        icon: "mdi-robot-angry-outline",
-        color: "green",
-    },
     {
         name: "Online Multiplayer",
         icon: "mdi-web",
         color: "blue",
+        componentName: "OnlineMode"
     },
 ]
 </script>