Refactor layout components and add loading state

- Refactor the layout components to improve code organization and readability.
- Add a new store called LoadingStore to manage the loading state.
- Update AppLayout.vue, AppMenu.vue, AppTopbar.vue, ScenarioStore.js, and UserPrefStore.js to import and use the LoadingStore.
- Add loading indicators in AppTopbar.vue and ScenarioList.vue components.

src/stores/UserPrefStore.js

@@ -1,19 +1,24 @@
 import { useAuth } from '@websanova/vue-auth/src/v3.js';
 import { defineStore } from 'pinia';
 import { computed, ref } from 'vue';
+import { LoadingStore } from './LoadingStore';
+
 export const UserPrefStore = defineStore('userpref_store', () => {
 
     const user = ref(null)
     const userLoaded = ref(false)
     const selectedApp = ref(null)
+    const loadingStore = LoadingStore()
+
 
     async function fetchUserData(){
       
       const auth = useAuth();
-
+      loadingStore.user_loading = true;
       await auth.fetch().then((fetchedUser) => {
           user.value = fetchedUser.data.data;
           userLoaded.value = true;
+          loadingStore.user_loading = false;
       }).catch((error) => {
           reject(error);
       });