添加数据备份和快捷查询优化

app/static/app.js

@@ -362,7 +362,7 @@ async function fetchJson(url) {
 async function loadHealth() {
   try {
     const data = await fetchJson("/api/health");
-    healthText.textContent = `课程记录 ${data.records_count} 条；数据更新时间 ${fmtTime(data.classnotes.mtime)}`;
+    healthText.textContent = `数据更新时间 ${fmtTime(data.classnotes.mtime)}`;
   } catch (error) {
     healthText.textContent = `读取失败：${error.message}`;
   }

app/static/index.html

@@ -26,6 +26,8 @@
           <h2>上课记录</h2>
           <div class="quick-actions">
             <button class="chip" data-query="今天上课记录" type="button">今天</button>
+            <button class="chip" data-query="昨天上课记录" type="button">昨天</button>
+            <button class="chip" data-query="前天上课记录" type="button">前天</button>
             <button class="chip" data-query="上周末上课记录" type="button">上周末</button>
           </div>
         </div>
@@ -110,6 +112,6 @@
       </section>
     </div>
 
-    <script src="/static/app.js?v=20260611-weekend-shortcuts"></script>
+    <script src="/static/app.js?v=20260612-relative-shortcuts"></script>
   </body>
 </html>