fix: surface Spotify quota exhaustion

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/components/StreamError.vue

@@ -8,7 +8,9 @@ defineEmits<{ retry: [] }>()
 <template>
   <div class="error" role="alert" :data-error-code="code">
     <p>{{ message }}</p>
-    <button type="button" @click="$emit('retry')">{{ messages.streamErrorRetry }}</button>
+    <button v-if="code !== 'quota_exhausted'" type="button" @click="$emit('retry')">
+      {{ messages.streamErrorRetry }}
+    </button>
     <a v-if="demoUrl" class="demo-link" :href="demoUrl">
       {{ messages.streamErrorDemoInstance }}
     </a>