docs: 统一导航菜单中"待处理预约"的文案

将多个页面导航菜单中的"待预约处理"统一修改为"待处理预约"，保持文案一致性

packages.php

@@ -78,7 +78,7 @@ $packages = $stmt->fetchAll();
             <nav class="nav">
                 <a href="index.php" class="nav-link">预约洗车</a>
                 <a href="bookings.php" class="nav-link">预约管理</a>
-                <a href="pending_bookings.php" class="nav-link">待预约处理</a>
+                <a href="pending_bookings.php" class="nav-link">待处理预约</a>
                 <a href="packages.php" class="nav-link active">套餐管理</a>
                 <a href="vip.php" class="nav-link">VIP管理</a>
                 <a href="announcement.php" class="nav-link">今日待办</a>