fix: hold gif thumbnails until first frame is ready

Distinguish GIF frame loading from GIF frame failure in useFetchGifFirstFrame(), so thread and catalog thumbnails no longer render animated GIFs before the still frame arrives. Keep the existing animated fallback when the first-frame fetch actually fails.

src/lib/utils/media-utils.ts

@@ -19,6 +19,8 @@ export const getDisplayMediaInfoType = (type: string, t: any) => {
   switch (type) {
     case 'image':
       return t('image');
+    case 'gif':
+      return t('gif');
     case 'animated gif':
       return t('animated_gif');
     case 'static gif':