修复我的收藏/查找聊天记录加载失败时卡死在"加载中…"，没有任何错误提示或重试入口

根因：Favorites 和 History（content-library-view.jsx）两个组件的 load() 里，请求失败的
.catch() 只调用 onToast() 弹一条 2 秒自动消失的提示，从未把 items 从初始值 null 变成别的
状态；页面渲染逻辑是"items === null 就显示'加载中…'"，两者叠加导致一次真实失败之后页面永远
停在"加载中…"，等用户反应过来去看的时候提示早就消失了，分不清"还在加载"和"永远不会加载完"。
这个坑本文件自己的 DownloadPage、group-management-view.jsx 的 GroupFiles、
contact-management-view.jsx 的 Profile 三处早就各自修过（都有一个独立的 loadError 状态），
唯独 Favorites/History 这两个用得最多的列表页当时漏掉了。

真实触发场景：用两个全新账号互加好友、发送图片/视频/文件/语音/文本等真实消息并收藏后，
发现收藏一条较大的（out-of-band）文件附件之后，GET /favorites?type=all 从此稳定返回
500 INTERNAL_ERROR（已确认是纯后端问题，不在前端能修的范围内，另行记录）——但这个后端
问题一暴露出来，"我的收藏"默认落地的"全部"tab 就会用真实数据 100% 复现这里描述的前端缺口：
打开就卡在"加载中…"，没有任何办法知道发生了什么、也无法重试。

修复：Favorites/History 都新增 loadError 状态，非 append（首次/切换 tab、类型、搜索词）请求
失败时置为 true、成功时置回 false，切换 type/topic/view/query 时重置；渲染时 items === null
且 loadError 为真则显示"加载失败，请重试"而不是死等的"加载中…"。"加载更多"（append）请求
失败保持原样只弹 toast，不影响已经显示出来的列表。

验证：复现上述 500 场景（GET /favorites?type=all 持续 500），修复前"我的收藏"全部 tab
永久停在"加载中…"；重新构建后同一账号同一坏数据状态下正确显示"加载失败，请重试"。

src/views/content-library-view.jsx

@@ -290,6 +290,16 @@ function Favorites({view, hashParams, tinode, onToast}) {
   const [items, setItems] = React.useState(() => readCachedData('favorites:' + type) || null);
   const [cursor, setCursor] = React.useState('');
   const [hasMore, setHasMore] = React.useState(false);
+  // A failed initial load (no cached list to fall back on) previously left this stuck on "加载中…"
+  // forever -- the catch handler only fired a toast, which fades in 2s, and `items` never left null
+  // so the loading branch below never had anything else to show. Same fix already applied to this
+  // file's own DownloadPage/GroupFiles(group-management-view.jsx)/Profile(contact-management-view.jsx)
+  // for the identical reason; Favorites/History were missed. Concretely hit live: favoriting a large
+  // (out-of-band) file attachment makes the *server* 500 on GET /favorites?type=all from then on
+  // (a real backend bug, tracked separately -- not something the frontend can prevent), and every
+  // subsequent visit to "全部" silently hung on the loading spinner with only a 2s toast, no way to
+  // tell "still loading" from "never going to load", no retry affordance.
+  const [loadError, setLoadError] = React.useState(false);
   const [fileUrls, setFileUrls] = React.useState({});
   const [sourceNames, setSourceNames] = React.useState({});
   // An in-flight request isn't guaranteed to resolve before a newer one its own type/query change
@@ -302,6 +312,7 @@ function Favorites({view, hashParams, tinode, onToast}) {
     const requestId = ++requestIdRef.current;
     getFavorites({type, query, cursor: append ? cursor : ''}).then(data => {
       if (requestIdRef.current !== requestId) return;
+      setLoadError(false);
       setItems(prev => {
         const list = append ? (prev || []).concat(data.items || []) : (data.items || []);
         if (!query) writeCachedData('favorites:' + type, list);
@@ -309,9 +320,14 @@ function Favorites({view, hashParams, tinode, onToast}) {
       });
       setCursor(data.next_cursor || '');
       setHasMore(!!data.next_cursor);
-    }).catch(err => onToast(err.message || '加载失败'));
+    }).catch(err => {
+      if (requestIdRef.current !== requestId) return;
+      onToast(err.message || '加载失败');
+      if (!append) setLoadError(true);
+    });
   }, [type, query, cursor]);
   React.useEffect(() => {
+    setLoadError(false);
     setItems((!query && readCachedData('favorites:' + type)) || null);
     load(false);
   }, [type, query]);
@@ -380,7 +396,7 @@ function Favorites({view, hashParams, tinode, onToast}) {
       // 类型列表内的勾选，没有跨 tab 累加的设计）。
       onClick={() => { setType(id); setSelected([]); if (TYPE_ROUTE[id] && !selecting) navigateReplace(TYPE_ROUTE[id]); }}>{label}</button>)}</nav>
     <main className="library-favorite-list">
-      {items === null ? <p className="library-empty-hint">加载中…</p> :
+      {items === null ? <p className="library-empty-hint">{loadError ? '加载失败，请重试' : '加载中…'}</p> :
         list.length ? <>{list.map(item => <FavoriteItem key={item.favorite_id} item={{...item, _thumbUrl: fileUrls[item.favorite_id],
             source_display: sourceNames[item.source && item.source.topic]}}
             selecting={selecting} selected={selected.includes(item.favorite_id)} onSelect={() => toggle(item.favorite_id)}
@@ -614,6 +630,10 @@ function History({view, hashParams, myUserId, onToast}) {
   const [items, setItems] = React.useState(() => (cacheKey && readCachedData(cacheKey)) || null);
   const [cursor, setCursor] = React.useState('');
   const [hasMore, setHasMore] = React.useState(false);
+  // Same "stuck on 加载中… forever" gap as Favorites' loadError above, same fix -- a failed initial
+  // load with nothing cached to fall back on left this on the loading branch permanently, with only
+  // a 2s toast (already faded by the time anyone looks back) as the only sign anything went wrong.
+  const [loadError, setLoadError] = React.useState(false);
   const [mediaUrls, setMediaUrls] = React.useState({});
   const [senderNames, setSenderNames] = React.useState({});
   // Same stale-response guard as Favorites' load() above and for the same reason -- a slower
@@ -628,15 +648,21 @@ function History({view, hashParams, myUserId, onToast}) {
       getTopicMedia(topic, type, append ? cursor : '');
     call.then(data => {
       if (requestIdRef.current !== requestId) return;
+      setLoadError(false);
       setItems(prev => {
         const list = append ? (prev || []).concat(data.items || []) : (data.items || []);
         if (!query && cacheKey) writeCachedData(cacheKey, list);
         return list;
       });
       setCursor(data.next_cursor || ''); setHasMore(!!data.next_cursor);
-    }).catch(err => onToast(err.message || '加载失败'));
+    }).catch(err => {
+      if (requestIdRef.current !== requestId) return;
+      onToast(err.message || '加载失败');
+      if (!append) setLoadError(true);
+    });
   }, [topic, view, query, cursor]);
   React.useEffect(() => {
+    setLoadError(false);
     setItems((!query && cacheKey && readCachedData(cacheKey)) || null);
     load(false);
   }, [topic, view, query]);
@@ -687,7 +713,7 @@ function History({view, hashParams, myUserId, onToast}) {
     {view === 'history-search' ? <Search value={queryInput} onChange={setQueryInput} placeholder="搜索当前会话" /> : null}
     <HistoryNav active={view} />
     <main className="library-history-content">
-      {items === null ? <p className="library-empty-hint">加载中…</p> : !list.length ?
+      {items === null ? <p className="library-empty-hint">{loadError ? '加载失败，请重试' : '加载中…'}</p> : !list.length ?
         <div className="library-empty"><Icon>{view === 'history-search' ? 'search_off' : 'inbox'}</Icon><strong>暂无内容</strong></div> :
       view === 'history-search' ? <section className="library-message-results">
         {/* 同一处"问题13"修复暴露的缺口，History 自己的一份，只影响 type==='text'：非 text 类型