Integrate Vuetify layout and routing

Add a Vuetify-powered application shell (Layout.vue) replacing the previous App.vue, including app bar, navigation drawer, theme toggle, footer and localStorage persistence for theme/drawer. Introduce a routesLayout plugin with a Visibility enum and centralized LayoutRoute definitions; add route components (Home, Impressum, Login, 404NotFound) and update the router to build routes from the new layout definitions. Register Vuetify in main.ts and add dependencies (vuetify, @fontsource/roboto, @mdi/font) in package.json; update tsconfig.app.json to include .ts files. Package-lock.json updated accordingly.

GUI/src/routes/Impressum.vue

@@ -0,0 +1,19 @@
+<script setup lang="ts"></script>
+
+<template>
+  <v-container class="py-10">
+    <v-row justify="center">
+      <v-col cols="12" md="10" lg="8">
+        <v-card rounded="lg" elevation="2">
+          <v-card-title class="text-h5">Impressum</v-card-title>
+          <v-card-text>
+            Diese Seite ist als Platzhalter angelegt. Trage hier deine Firmen- oder Vereinsdaten
+            ein.
+          </v-card-text>
+        </v-card>
+      </v-col>
+    </v-row>
+  </v-container>
+</template>
+
+<style scoped></style>