fix: web dashboard Reader fetches article content on select

Slim list mode means list responses no longer include content.
Now selectArticle() fetches the full entry via GET /entries/{id}
before displaying, then optionally crawls for full content if short.
Also uses API thumbnail field instead of extracting from empty content.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend-v2/src/lib/pages/reader/AtelierReaderPage.svelte

@@ -62,7 +62,7 @@
     return {
       id: e.id, title: e.title, feed: e.feed?.title || '', url: e.url,
       timeAgo: timeAgo(e.published_at), readingTime: `${e.reading_time || 1} min`,
-      content: e.content || '', thumbnail: extractThumb(e.content),
+      content: e.content || '', thumbnail: e.thumbnail || extractThumb(e.content),
       starred: e.starred || false, read: e.status === 'read',
       author: e.author || ''
     };
@@ -305,10 +305,25 @@
       markEntryRead(article.id);
       decrementUnread();
     }
-    // Auto-fetch full article content if we only have RSS summary
-    if (article.content && article.content.length < 1500) {
-      fetchFullContent(article);
-    }
+    // Fetch full entry content (slim list doesn't include it)
+    loadArticleContent(article);
+  }
+
+  async function loadArticleContent(article: Article) {
+    try {
+      const data = await api(`/entries/${article.id}`);
+      const content = data.full_content || data.content || '';
+      article.content = content;
+      if (data.thumbnail) article.thumbnail = data.thumbnail;
+      if (selectedArticle?.id === article.id) {
+        selectedArticle = { ...article };
+      }
+      articles = [...articles];
+      // If content is short, try fetching full article via crawler
+      if (content.length < 1500) {
+        fetchFullContent(article);
+      }
+    } catch { /* silent */ }
   }
 
   async function fetchFullContent(article: Article) {