Handle missing Spotify auth gracefully instead of returning errors

Return nil/empty results when Spotify client is not authenticated,
preventing GraphQL errors from breaking the home page data query.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vue/src/stores/homeData.js

@@ -35,7 +35,7 @@ export const useHomeDataStore = defineStore("homeData", () => {
       posts.value = data.posts;
       favorites.value = data.favorites;
       activities.value = data.activities;
-      spotifyRecent.value = data.spotifyRecent;
+      spotifyRecent.value = data.spotifyRecent || [];
       rowingSessions.value = data.rowingSessions;
       gitFeed.value = data.giteaFeed || null;
       me.value = data.me || null;