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/main.ts

@@ -1,6 +1,6 @@
 import { createApp } from 'vue'
 import App from './Layout.vue'
-import router from './utils'
+import router from './router'
 // Vuetify
 import 'vuetify/styles'
 import { createVuetify } from 'vuetify'
@@ -22,6 +22,8 @@ import '@fontsource/roboto/700-italic.css'
 import '@fontsource/roboto/900-italic.css'
 // Icons
 import '@mdi/font/css/materialdesignicons.css'
+// Styles
+import "./app.css"
 
 // Vuetify
 const vuetify = createVuetify({