feat: implement dark mode handling and improve embedded page layout logic

Author: tacxou

src/app.vue

@@ -6,9 +6,17 @@
 </template>
 
 <script lang="ts" setup>
+const $q = useQuasar()
 const $route = useRoute()
 
 if (/1|yes|on|true/.test($route.query.embedded as string)) {
   setPageLayout('empty')
 }
+
+const darkMode = window.sessionStorage.getItem('darkMode')
+if (typeof darkMode === 'string') {
+  $q.dark.set(/true|1|on/.test(darkMode))
+} else {
+  window.sessionStorage.setItem('darkMode', $q.dark.isActive ? 'true' : 'false')
+}
 </script>