feat: allow running elk with a single server (#1606)

components/user/UserSignInEntry.vue

@@ -1,3 +1,7 @@
+<script setup lang="ts">
+const { busy, oauth, singleInstanceServer } = useSignIn()
+</script>
+
 <template>
   <div p8 lg:flex="~ col gap2" hidden>
     <p v-if="isHydrated" text-sm>
@@ -8,7 +12,19 @@
     <p text-sm text-secondary>
       {{ $t('user.sign_in_desc') }}
     </p>
-    <button btn-solid rounded-3 text-center mt-2 select-none @click="openSigninDialog()">
+    <button
+      v-if="singleInstanceServer"
+      flex="~ row" gap-x-2 items-center justify-center btn-solid text-center rounded-3
+      :disabled="busy"
+      @click="oauth()"
+    >
+      <span v-if="busy" aria-hidden="true" block animate animate-spin preserve-3d class="rtl-flip">
+        <span block i-ri:loader-2-fill aria-hidden="true" />
+      </span>
+      <span v-else aria-hidden="true" block i-ri:login-circle-line class="rtl-flip" />
+      {{ $t('action.sign_in') }}
+    </button>
+    <button v-else btn-solid rounded-3 text-center mt-2 select-none @click="openSigninDialog()">
       {{ $t('action.sign_in') }}
     </button>
   </div>