fix: replace weread:// deep link with web URL for 'Open in WeRead' button

The hardcoded 'weread://reading?bId=...' scheme only works on mobile
devices with the WeRead app installed. On desktop browsers, clicking
the button did nothing. Now uses data.deep_link from the API response
(https://weread.qq.com/...) with fallback logic: try weread:// scheme
via hidden iframe for 1.5s, then fall back to opening the web URL.

static/js/app.js

@@ -155,6 +155,44 @@ function scrollToTop() {
     window.scrollTo({ top: 0, behavior: "smooth" });
 }
 
+/**
+ * 在微信读书中打开书籍。
+ * 优先使用 API 返回的 deep_link（https://weread.qq.com/... 网页链接），
+ * 没有则用 book_id 构造网页链接。先尝试 weread:// 深链接唤起 App，
+ * 1.5 秒后无响应则回退到网页版。
+ */
+function openInWeRead(bookId, deepLink) {
+    const webUrl = deepLink || `https://weread.qq.com/#book/${bookId}`;
+    const schemeUrl = `weread://reading?bId=${bookId}`;
+
+    // 尝试唤起 App（移动端），同时设置定时器回退到网页版
+    let triggered = false;
+    const fallbackTimer = setTimeout(() => {
+        if (!triggered) window.open(webUrl, "_blank");
+    }, 1500);
+
+    // 监听页面可见性变化（App 唤起成功会切到后台）
+    const onVisChange = () => {
+        if (document.hidden) {
+            triggered = true;
+            clearTimeout(fallbackTimer);
+        }
+    };
+    document.addEventListener("visibilitychange", onVisChange);
+
+    // 尝试打开深链接
+    const iframe = document.createElement("iframe");
+    iframe.style.display = "none";
+    iframe.src = schemeUrl;
+    document.body.appendChild(iframe);
+    setTimeout(() => document.body.removeChild(iframe), 2000);
+
+    // 桌面端不会有 visibilitychange，确保 fallback 一定执行
+    setTimeout(() => {
+        document.removeEventListener("visibilitychange", onVisChange);
+    }, 3000);
+}
+
 // ===== 全局搜索（顶部常驻搜索框） =====
 
 function globalSearch() {
@@ -728,7 +766,7 @@ function openBook(bookId) {
                     ${data.word_count ? `<div class="detail-info-item"><strong>字数:</strong> ${(data.word_count / 10000).toFixed(1)}万字</div>` : ''}
                 </div>
                 <div class="detail-actions">
-                    <button class="btn-primary" onclick="window.open('weread://reading?bId=${bookId}','_blank')">在微信读书中打开</button>
+                    <button class="btn-primary" onclick="openInWeRead('${bookId}', ${data.deep_link ? `'${data.deep_link}'` : 'null'})">在微信读书中打开</button>
                     <button class="btn-primary detail-action-thoughts" onclick="closeModal('bookDetailModal');openThoughtsPage('${bookId}', '${(data.title || '').replace(/'/g, "\\'")}', '${(data.author || '').replace(/'/g, "\\'")}', '${data.cover || ''}')">📖 查看想法</button>
                 </div>
             `;