fix: Dark mode not working on dark browsers

Ironically, only if browser preference and wall config agreed both on dark mode,
it was not applied because there was no change detected by watch().

src/App.vue

@@ -59,7 +59,7 @@ const actualTheme = computed(() => {
 })
 watch(actualTheme, () => {
   document.body!.parentElement!.dataset.bsTheme = actualTheme.value
-})
+}, {immediate: true})
 
 // Update page title
 watch(() => config.value?.title, () => document.title = config.value?.title || fallbackConfig.title)