修复总收入计算逻辑，确保金额正确处理为数字类型，并更新显示格式以保持一致性。

app/admin/page.tsx

@@ -63,7 +63,7 @@ export default function AdminDashboard() {
     )
   }
 
-  const totalRevenue = purchases.reduce((sum, p) => sum + (p.amount || 0), 0)
+  const totalRevenue = purchases.reduce((sum, p) => sum + Number(p.amount || 0), 0)
   const totalUsers = users.length
   const totalPurchases = purchases.length
 
@@ -71,7 +71,7 @@ export default function AdminDashboard() {
     { title: "总用户数", value: totalUsers, icon: Users, color: "text-blue-400", bg: "bg-blue-500/20", link: "/admin/users" },
     {
       title: "总收入",
-      value: `¥${totalRevenue.toFixed(2)}`,
+      value: `¥${Number(totalRevenue).toFixed(2)}`,
       icon: TrendingUp,
       color: "text-[#38bdac]",
       bg: "bg-[#38bdac]/20",