Fix: Move composables and components into app/ directory

- Resolve SSR error "useAuthentik is not defined"
- Follow Nuxt 4 directory structure conventions
- When app/ exists, all app directories must be inside it
- This enables proper auto-import of composables

nuxt4/app/components/auth/UserAvatar.vue

@@ -0,0 +1,20 @@
+<template>
+  <UCard v-if="user" class="w-full">
+    <div class="flex items-center gap-4">
+      <UAvatar
+        :src="user.avatar"
+        :alt="user.name || user.username"
+        size="xl"
+      />
+      <div class="flex-1">
+        <h3 class="font-semibold text-lg">{{ user.name || user.username }}</h3>
+        <p class="text-sm text-gray-500 dark:text-gray-400">{{ user.email }}</p>
+        <p class="text-xs text-gray-400 dark:text-gray-500 mt-1">ID: {{ user.uid }}</p>
+      </div>
+    </div>
+  </UCard>
+</template>
+
+<script setup lang="ts">
+const { user } = useAuthentik()
+</script>