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/pages/profile.vue

@@ -16,23 +16,7 @@
         </template>
         <template v-else-if="me">
           <div class="flex flex-wrap items-center gap-4">
-            <div class="avatar">
-              <div class="rounded-full w-14 h-14 overflow-hidden flex items-center justify-center">
-                <img
-                  v-if="me.email && !gravatarError"
-                  :src="useGravatarUrl(me.email, 80)"
-                  alt=""
-                  class="w-full h-full object-cover"
-                  @error="gravatarError = true"
-                >
-                <div
-                  v-else
-                  class="bg-primary text-primary-content rounded-full w-14 h-14 flex items-center justify-center"
-                >
-                  <span class="text-2xl font-semibold">{{ (me.username || '?')[0].toUpperCase() }}</span>
-                </div>
-              </div>
-            </div>
+            <UserAvatar :username="me.username" :email="me.email" :size="56" />
             <div class="flex flex-col gap-1">
               <h2 class="text-lg font-semibold">{{ me.username }}</h2>
               <div class="flex flex-wrap gap-1.5">
@@ -159,7 +143,6 @@ const passMsg = ref('')
 const passOk = ref(false)
 const tokenError = ref('')
 const copiedToken = ref<string | null>(null)
-const gravatarError = ref(false)
 const emailEditing = ref(false)
 const emailEdit = ref('')
 const loadingEmail = ref(false)
@@ -185,7 +168,6 @@ async function saveEmail() {
     const data = await api.me()
     me.value = data
     emailEditing.value = false
-    gravatarError.value = false
     toast.success('Email updated')
   } catch (e: unknown) {
     emailError.value = e instanceof Error ? e.message : 'Failed to update email'