Refactor frontend components and enhance API integration

- Updated frontend-nuxt.mdc to specify usage of composables for API calls.
- Added new AuthCard and ConfirmModal components for improved UI consistency.
- Introduced UserAvatar component for user profile display, replacing previous Gravatar implementation.
- Implemented useFormSubmit composable for handling form submissions with loading and error states.
- Enhanced vitest.config.ts to include coverage reporting for composables and components.
- Removed deprecated useAdminApi and useAuth composables to streamline API interactions.
- Updated login and setup pages to utilize new components and composables for better user experience.

frontend-nuxt/components/AuthCard.vue

@@ -0,0 +1,12 @@
+<template>
+  <div class="min-h-screen flex flex-col items-center justify-center bg-gradient-to-br from-base-200 via-base-300 to-primary/10 p-4 overflow-hidden">
+    <div class="card card-app w-full max-w-sm login-card">
+      <div class="card-body">
+        <slot />
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+</script>