fix(admin): auto-expand sidebar navigation group for active child page

- Add getExpandedMenusForPath to auto-expand the parent menu group
  when navigating to a child page (e.g., /admin/users expands "系统管理")
- Add hasActiveChild highlight on parent menu group button (bg-gray-100)
- Use lazy initialization for expandedMenus state based on current path
- Use useEffect to track pathname changes and auto-expand accordingly
- Replace `path` unused param with `_path` to satisfy TypeScript strict

src/components/admin/admin-layout.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { useState } from 'react';
+import { useState, useEffect, useRef } from 'react';
 import Link from 'next/link';
 import { usePathname, useRouter } from 'next/navigation';
 import { useAuth } from './auth-context';
@@ -82,11 +82,48 @@ const menuItems = [
 
 export function AdminLayout({ children }: { children: React.ReactNode }) {
   const [sidebarOpen, setSidebarOpen] = useState(false);
-  const [expandedMenus, setExpandedMenus] = useState<Set<string>>(new Set(['内容管理']));
   const { user, logout } = useAuth();
   const pathname = usePathname();
   const router = useRouter();
 
+  const isActive = (href: string) => pathname === href || pathname?.startsWith(href + '/');
+
+  /**
+   * 根据当前路径自动展开对应的父菜单组
+   */
+  const getExpandedMenusForPath = (_path: string): Set<string> => {
+    const result = new Set<string>();
+    for (const group of menuItems) {
+      for (const item of group.children) {
+        if (isActive(item.href)) {
+          result.add(group.label);
+          break;
+        }
+      }
+    }
+    // 若当前路径在某个组内，保留已有展开状态并追加；否则保留默认展开
+    if (result.size > 0) {
+      return result;
+    }
+    return new Set(['内容管理']);
+  };
+
+  const [expandedMenus, setExpandedMenus] = useState<Set<string>>(() => getExpandedMenusForPath(pathname));
+
+  // 路径变化时自动展开对应父菜单组
+  const prevPathname = useRef(pathname);
+  useEffect(() => {
+    if (prevPathname.current !== pathname) {
+      prevPathname.current = pathname;
+      const menusForPath = getExpandedMenusForPath(pathname);
+      setExpandedMenus((prev) => {
+        const next = new Set(prev);
+        menusForPath.forEach((label) => next.add(label));
+        return next;
+      });
+    }
+  }, [pathname]);
+
   const toggleMenu = (label: string) => {
     setExpandedMenus((prev) => {
       const next = new Set(prev);
@@ -101,8 +138,6 @@ export function AdminLayout({ children }: { children: React.ReactNode }) {
     router.push('/admin/login');
   };
 
-  const isActive = (href: string) => pathname === href || pathname?.startsWith(href + '/');
-
   return (
     <div className="min-h-screen bg-gray-50">
       {/* Mobile overlay */}
@@ -146,11 +181,17 @@ export function AdminLayout({ children }: { children: React.ReactNode }) {
           </Link>
 
           {/* Menu groups */}
-          {menuItems.map((group) => (
+          {menuItems.map((group) => {
+            const hasActiveChild = group.children.some((item) => isActive(item.href));
+            return (
             <div key={group.label}>
               <button
                 onClick={() => toggleMenu(group.label)}
-                className="flex items-center justify-between w-full px-3 py-2.5 rounded-lg text-sm font-medium text-gray-600 hover:bg-gray-100 transition-colors"
+                className={`flex items-center justify-between w-full px-3 py-2.5 rounded-lg text-sm font-medium transition-colors ${
+                  hasActiveChild
+                    ? 'bg-gray-100 text-gray-900'
+                    : 'text-gray-600 hover:bg-gray-100'
+                }`}
               >
                 <span className="flex items-center gap-3">
                   <group.icon className="w-4 h-4" />
@@ -182,7 +223,8 @@ export function AdminLayout({ children }: { children: React.ReactNode }) {
                 </div>
               )}
             </div>
-          ))}
+            );
+          })}
         </nav>
 
         {/* User info */}