feat(ui): add Lobby and Main Menu Body (#38)

Co-authored-by: LQ63 <lkhermann@web.de>
Reviewed-on: #38
Co-authored-by: Janis <janis.e.20@gmx.de>
Co-committed-by: Janis <janis.e.20@gmx.de>

knockoutwhistweb/app/assets/stylesheets/dark-mode.less

@@ -1,6 +1,13 @@
 @media (prefers-color-scheme: dark) {
   :root {
     --background-image: url('/assets/images/background.png');
-    --color: white;
+    --color: #f8f9fa; /* Light text on dark bg */
+
+    /* Bootstrap variable overrides for dark mode */
+    --bs-body-color: var(--color);
+    --bs-link-color: #66b2ff;
+    --bs-link-hover-color: #99ccff;
+    --bs-border-color: rgba(255, 255, 255, 0.2);
+    --bs-heading-color: var(--color);
   }
 }