feat(admin): enhance admin dashboard, user management, and content editor UX

- Dashboard: add stats API with content status distribution, recent notifications,
  and recent content updates; display active users, pending reviews, unread counts
- User management: full CRUD with role assignment, search, pagination, delete dialog
- Notification center: list with unread filter, mark as read, mark all as read,
  pagination, and auto-refresh unread count
- Content editor: form validation (required fields, slug format, blur-triggered
  errors), auto-save with 3s debounce and status indicator, publish confirmation
  dialog, unsaved changes warning on leave
- Admin layout: add navigation links for user management, roles, and notifications
- admin-api: make request() method public for custom API calls
- gitignore: add reports/mutation/ to exclude mutation test output

src/app/admin/notifications/page.tsx

@@ -0,0 +1,320 @@
+'use client';
+
+import { useEffect, useState, useCallback } from 'react';
+import { useRouter } from 'next/navigation';
+import { useAuth } from '@/components/admin/auth-context';
+import { adminApi } from '@/lib/admin-api';
+import { toast } from '@/components/ui/sonner';
+import {
+  Bell,
+  CheckCheck,
+  Mail,
+  MailOpen,
+  Clock,
+  AlertCircle,
+  CheckCircle,
+  XCircle,
+  Archive,
+  ExternalLink,
+  RefreshCw,
+} from 'lucide-react';
+
+interface NotificationItem {
+  id: string;
+  type: string;
+  title: string;
+  message: string;
+  read: boolean;
+  relatedItemId: string;
+  relatedModelCode: string;
+  createdAt: string;
+}
+
+const NOTIFICATION_TYPE_LABELS: Record<string, string> = {
+  review_pending: '待审核',
+  review_approved: '审核通过',
+  review_rejected: '审核驳回',
+  item_archived: '已归档',
+};
+
+const NOTIFICATION_TYPE_ICONS: Record<string, React.ReactNode> = {
+  review_pending: <AlertCircle className="w-4 h-4 text-amber-500" />,
+  review_approved: <CheckCircle className="w-4 h-4 text-green-500" />,
+  review_rejected: <XCircle className="w-4 h-4 text-red-500" />,
+  item_archived: <Archive className="w-4 h-4 text-gray-500" />,
+};
+
+const NOTIFICATION_TYPE_COLORS: Record<string, string> = {
+  review_pending: 'bg-amber-50 border-amber-200',
+  review_approved: 'bg-green-50 border-green-200',
+  review_rejected: 'bg-red-50 border-red-200',
+  item_archived: 'bg-gray-50 border-gray-200',
+};
+
+export default function NotificationsPage() {
+  const { user, loading: authLoading } = useAuth();
+  const router = useRouter();
+
+  const [notifications, setNotifications] = useState<NotificationItem[]>([]);
+  const [total, setTotal] = useState(0);
+  const [page, setPage] = useState(1);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState('');
+  const [unreadOnly, setUnreadOnly] = useState(false);
+  const [unreadCount, setUnreadCount] = useState(0);
+  const pageSize = 20;
+
+  const fetchNotifications = useCallback(async () => {
+    setLoading(true);
+    setError('');
+    try {
+      const query = new URLSearchParams();
+      query.set('page', String(page));
+      query.set('pageSize', String(pageSize));
+      if (unreadOnly) query.set('unreadOnly', 'true');
+
+      const data = await adminApi.request<{
+        items: NotificationItem[];
+        total: number;
+        page: number;
+        pageSize: number;
+        totalPages: number;
+      }>(`/api/admin/notifications?${query.toString()}`);
+      setNotifications(data.items || []);
+      setTotal(data.total || 0);
+    } catch (err) {
+      setError(err instanceof Error ? err.message : '加载失败');
+    } finally {
+      setLoading(false);
+    }
+  }, [page, unreadOnly]);
+
+  const fetchUnreadCount = useCallback(async () => {
+    try {
+      const data = await adminApi.request<{ count: number }>('/api/admin/notifications/unread-count');
+      setUnreadCount(data.count || 0);
+    } catch {
+      // Non-critical
+    }
+  }, []);
+
+  useEffect(() => {
+    if (!authLoading && !user) {
+      router.push('/admin/login');
+      return;
+    }
+    if (user) {
+      fetchNotifications();
+      fetchUnreadCount();
+    }
+  }, [user, authLoading, router, fetchNotifications, fetchUnreadCount]);
+
+  const handleMarkAsRead = async (id: string) => {
+    try {
+      await adminApi.request(`/api/admin/notifications/${id}/read`, { method: 'POST' });
+      setNotifications((prev) =>
+        prev.map((n) => (n.id === id ? { ...n, read: true } : n))
+      );
+      setUnreadCount((prev) => Math.max(0, prev - 1));
+    } catch {
+      toast.error('标记已读失败');
+    }
+  };
+
+  const handleMarkAllAsRead = async () => {
+    try {
+      await adminApi.request('/api/admin/notifications/read-all', { method: 'POST' });
+      setNotifications((prev) => prev.map((n) => ({ ...n, read: true })));
+      setUnreadCount(0);
+      toast.success('全部标记为已读');
+    } catch {
+      toast.error('操作失败');
+    }
+  };
+
+  const handleViewRelated = (item: NotificationItem) => {
+    if (item.relatedItemId && item.relatedModelCode) {
+      router.push(`/admin/content/${item.relatedModelCode}/${item.relatedItemId}`);
+    }
+  };
+
+  const totalPages = Math.ceil(total / pageSize);
+
+  if (authLoading || (!user && typeof window !== 'undefined')) {
+    return (
+      <div className="flex items-center justify-center h-64">
+        <div className="animate-spin w-8 h-8 border-2 border-gray-900 border-t-transparent rounded-full" />
+      </div>
+    );
+  }
+
+  return (
+    <div className="space-y-6">
+      <div className="flex items-center justify-between">
+        <div>
+          <h1 className="text-xl font-bold text-gray-900">通知中心</h1>
+          <p className="text-sm text-gray-500 mt-1">
+            共 {total} 条通知
+            {unreadCount > 0 && (
+              <span className="ml-2 inline-flex items-center px-2 py-0.5 rounded-full text-xs font-medium bg-red-100 text-red-700">
+                {unreadCount} 条未读
+              </span>
+            )}
+          </p>
+        </div>
+        <div className="flex items-center gap-2">
+          <button
+            onClick={() => { setUnreadOnly(!unreadOnly); setPage(1); }}
+            className={`flex items-center gap-2 px-3 py-2 rounded-lg text-sm font-medium border transition-colors ${
+              unreadOnly
+                ? 'bg-gray-900 text-white border-gray-900'
+                : 'bg-white text-gray-600 border-gray-200 hover:border-gray-400'
+            }`}
+          >
+            <Mail className="w-4 h-4" />
+            仅未读
+          </button>
+          {unreadCount > 0 && (
+            <button
+              onClick={handleMarkAllAsRead}
+              className="flex items-center gap-2 px-3 py-2 bg-white text-gray-600 rounded-lg text-sm font-medium border border-gray-200 hover:border-gray-400 transition-colors"
+            >
+              <CheckCheck className="w-4 h-4" />
+              全部已读
+            </button>
+          )}
+          <button
+            onClick={() => { fetchNotifications(); fetchUnreadCount(); }}
+            className="flex items-center gap-2 px-3 py-2 bg-white text-gray-600 rounded-lg text-sm font-medium border border-gray-200 hover:border-gray-400 transition-colors"
+          >
+            <RefreshCw className="w-4 h-4" />
+            刷新
+          </button>
+        </div>
+      </div>
+
+      {error && (
+        <div className="p-4 bg-red-50 border border-red-200 rounded-lg text-sm text-red-600">
+          {error}
+        </div>
+      )}
+
+      {/* Notifications list */}
+      <div className="space-y-2">
+        {loading ? (
+          <div className="flex items-center justify-center py-12 text-gray-400">
+            <div className="flex items-center gap-2">
+              <div className="animate-spin w-4 h-4 border-2 border-gray-400 border-t-transparent rounded-full" />
+              加载中...
+            </div>
+          </div>
+        ) : notifications.length === 0 ? (
+          <div className="flex flex-col items-center justify-center py-16 text-gray-400">
+            <Bell className="w-12 h-12 mb-3 text-gray-200" />
+            <p className="text-sm">暂无通知</p>
+            {unreadOnly && (
+              <p className="text-xs text-gray-300 mt-1">没有未读通知，试试查看全部</p>
+            )}
+          </div>
+        ) : (
+          notifications.map((item) => (
+            <div
+              key={item.id}
+              className={`relative flex items-start gap-4 p-4 rounded-lg border transition-colors ${
+                item.read
+                  ? 'bg-white border-gray-100'
+                  : NOTIFICATION_TYPE_COLORS[item.type] || 'bg-blue-50 border-blue-200'
+              }`}
+            >
+              {/* Unread indicator */}
+              {!item.read && (
+                <div className="absolute top-4 left-4 w-2 h-2 rounded-full bg-blue-500" />
+              )}
+
+              {/* Type icon */}
+              <div className={`flex-shrink-0 w-8 h-8 rounded-full flex items-center justify-center ${
+                item.read ? 'bg-gray-100' : 'bg-white'
+              }`}>
+                {NOTIFICATION_TYPE_ICONS[item.type] || <Bell className="w-4 h-4 text-gray-400" />}
+              </div>
+
+              {/* Content */}
+              <div className="flex-1 min-w-0">
+                <div className="flex items-center gap-2 mb-1">
+                  <span className={`text-xs font-medium px-1.5 py-0.5 rounded ${
+                    item.read ? 'text-gray-500' : ''
+                  }`}>
+                    {NOTIFICATION_TYPE_LABELS[item.type] || item.type}
+                  </span>
+                  <span className="text-xs text-gray-400 flex items-center gap-1">
+                    <Clock className="w-3 h-3" />
+                    {new Date(item.createdAt).toLocaleString('zh-CN', {
+                      year: 'numeric',
+                      month: '2-digit',
+                      day: '2-digit',
+                      hour: '2-digit',
+                      minute: '2-digit',
+                    })}
+                  </span>
+                </div>
+                <h3 className={`text-sm font-medium ${item.read ? 'text-gray-600' : 'text-gray-900'}`}>
+                  {item.title}
+                </h3>
+                <p className={`text-xs mt-0.5 ${item.read ? 'text-gray-400' : 'text-gray-500'}`}>
+                  {item.message}
+                </p>
+
+                {/* Actions */}
+                <div className="flex items-center gap-3 mt-2">
+                  {!item.read && (
+                    <button
+                      onClick={() => handleMarkAsRead(item.id)}
+                      className="text-xs text-gray-500 hover:text-gray-700 flex items-center gap-1"
+                    >
+                      <MailOpen className="w-3 h-3" />
+                      标记已读
+                    </button>
+                  )}
+                  {item.relatedItemId && item.relatedModelCode && (
+                    <button
+                      onClick={() => handleViewRelated(item)}
+                      className="text-xs text-blue-600 hover:text-blue-800 flex items-center gap-1"
+                    >
+                      <ExternalLink className="w-3 h-3" />
+                      查看详情
+                    </button>
+                  )}
+                </div>
+              </div>
+            </div>
+          ))
+        )}
+      </div>
+
+      {/* Pagination */}
+      {totalPages > 1 && (
+        <div className="flex items-center justify-between px-4 py-3 bg-white rounded-lg border border-gray-200">
+          <span className="text-sm text-gray-500">
+            共 {total} 条，第 {page}/{totalPages} 页
+          </span>
+          <div className="flex items-center gap-2">
+            <button
+              onClick={() => setPage((p) => Math.max(1, p - 1))}
+              disabled={page <= 1}
+              className="px-3 py-1.5 text-sm rounded border border-gray-200 hover:bg-gray-100 disabled:opacity-50 disabled:cursor-not-allowed"
+            >
+              上一页
+            </button>
+            <button
+              onClick={() => setPage((p) => Math.min(totalPages, p + 1))}
+              disabled={page >= totalPages}
+              className="px-3 py-1.5 text-sm rounded border border-gray-200 hover:bg-gray-100 disabled:opacity-50 disabled:cursor-not-allowed"
+            >
+              下一页
+            </button>
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}