feat: add theme-color for modern browser (#599)

* feat: add `theme-color` for modern browser

* feat: add `theme-color` to login page

* refactor(meta): move `useHead` to `app.vue`

* style(theme-color): black for dark theme

Author: at-wr

app.vue

@@ -2,6 +2,13 @@
 import { ConfigProvider } from 'radix-vue'
 
 const useIdFunction = () => useId()
+
+useHead({
+  meta: [
+    { name: 'theme-color', media: '(prefers-color-scheme: light)', content: 'white' },
+    { name: 'theme-color', media: '(prefers-color-scheme: dark)', content: 'black' },
+  ],
+})
 </script>
 
 <template>