Add basic routing and layout structure

Replaced App.vue with Layout.vue to serve as the main layout. Added Home and 404NotFound route components and configured router to handle home and fallback routes. Updated main.ts to use the new layout component.

GUI/src/Layout.vue

@@ -0,0 +1,8 @@
+<script setup lang="ts"></script>
+
+<template>
+  <h1>You did it!</h1>
+  <router-view></router-view>
+</template>
+
+<style scoped></style>