书架恢复横向网格展示，移除分类分组标题

- loadShelf 始终用简单网格渲染，不再调用 renderBooksGroupedByCategory
- 删除 renderBooksGroupedByCategory 函数
- 清理 .shelf-group-header / .shelf-group-count CSS 样式
- 后端 sort=category 仍生效（按分类排序），前端不显示分组标题
- 分类筛选标签保留

.workbuddy/memory/2026-07-17.md

@@ -79,3 +79,11 @@
   3. 书架搜索支持书名/作者：/api/shelf 新增 keyword 参数（title LIKE OR author LIKE），原 category 改为精确匹配
   4. 分类标签栏：书架页显示所有分类的可点击标签（pill 样式），点击筛选对应分类
   5. 微信读书 CDN 封面前缀：t6_=低清(~150px), s_=超低清(~90px,搜索结果用), t8_=高清(~500px)
+
+## 12:27 移除分类排序按钮，默认按分类排序
+
+- 用户反馈：分类排序不需要前端按钮，默认生效即可
+- 删除 index.html 中的 shelfSortBtn 按钮
+- app.js 中 shelfSortMode 默认值从 "default" 改为 "category"
+- 删除 toggleShelfSort 函数和 .shelf-sort-btn CSS 样式
+- 书架列表始终按分类分组渲染，无需手动切换

static/css/style.css

@@ -447,33 +447,6 @@ body {
     color: #fff;
 }
 
-/* 分类分组标题 */
-.shelf-group-header {
-    font-size: 15px;
-    font-weight: 700;
-    color: var(--text-primary);
-    margin: 24px 0 12px;
-    padding: 8px 16px;
-    border-radius: var(--radius-sm);
-    background: var(--accent-bg);
-    border-left: 4px solid var(--accent);
-}
-
-.shelf-group-header:first-child {
-    margin-top: 0;
-}
-
-.shelf-group-count {
-    font-size: 12px;
-    font-weight: 400;
-    color: var(--text-light);
-    margin-left: 8px;
-}
-
-.shelf-group-header + .book-grid {
-    margin-bottom: 8px;
-}
-
 /* ===== Hero 区 ===== */
 .hero-section {
     position: relative;

static/js/app.js

@@ -690,14 +690,7 @@ async function loadShelf(page) {
         document.getElementById("shelfInfo").textContent =
             `共 ${data.total} 本 · 第 ${page}/${data.total_pages} 页`;
 
-        if (shelfSortMode === "category" && data.books.length > 0) {
+        grid.innerHTML = data.books.map((book) => renderBookCard(book)).join("");
-            // 按分类分组渲染
-            grid.innerHTML = renderBooksGroupedByCategory(data.books);
-        } else {
-            grid.innerHTML = data.books
-                .map((book) => renderBookCard(book))
-                .join("");
-        }
 
         renderPagination(page, data.total_pages);
     } catch (e) {
@@ -722,23 +715,6 @@ function renderBookCard(book) {
     </div>`;
 }
 
-function renderBooksGroupedByCategory(books) {
-    // 按 category 分组
-    const groups = {};
-    books.forEach((book) => {
-        const cat = book.category || "未分类";
-        if (!groups[cat]) groups[cat] = [];
-        groups[cat].push(book);
-    });
-
-    let html = "";
-    for (const [cat, items] of Object.entries(groups)) {
-        html += `<div class="shelf-group-header">${cat} <span class="shelf-group-count">${items.length} 本</span></div>`;
-        html += `<div class="book-grid">${items.map(renderBookCard).join("")}</div>`;
-    }
-    return html;
-}
-
 function renderPagination(current, total) {
     const pag = document.getElementById("pagination");
     if (total <= 1) { pag.innerHTML = ""; return; }