fix(auth): handle zero-permission users gracefully and prevent redirect loops

src/routes/_authed/index.tsx

@@ -1,7 +1,51 @@
-import { createFileRoute, redirect } from '@tanstack/react-router'
+import { createFileRoute, redirect, useNavigate } from '@tanstack/react-router'
+import { ShieldAlert, LogOut } from 'lucide-react'
+import { getFirstAccessibleRoute } from '@/components/layout/nav'
+import { useAuthStore } from '@/auth/store'
+import { Button } from '@/components/ui/button'
+import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
 
 export const Route = createFileRoute('/_authed/')({
   beforeLoad: () => {
-    throw redirect({ to: '/categories' })
+    const target = getFirstAccessibleRoute()
+    if (target && target !== '/') {
+      throw redirect({ to: target })
+    }
   },
+  component: DashboardIndexPage,
 })
+
+function DashboardIndexPage() {
+  const navigate = useNavigate()
+  const user = useAuthStore((s) => s.user)
+
+  const logout = () => {
+    useAuthStore.getState().clear()
+    void navigate({ to: '/login' })
+  }
+
+  return (
+    <div className="flex min-h-[60vh] items-center justify-center p-4">
+      <Card className="w-full max-w-md text-center shadow-xs">
+        <CardHeader>
+          <div className="mx-auto mb-2 flex size-12 items-center justify-center rounded-full bg-amber-500/10 text-amber-600 dark:bg-amber-500/20 dark:text-amber-400">
+            <ShieldAlert className="size-6" />
+          </div>
+          <CardTitle className="text-xl">账号未分配权限</CardTitle>
+          <CardDescription>
+            当前账号【{user?.display_name ?? user?.username ?? user?.uid}】尚未分配任何管理后台权限
+          </CardDescription>
+        </CardHeader>
+        <CardContent className="space-y-4">
+          <p className="text-xs text-muted-foreground">
+            如果您需要访问管理后台，请联系超级管理员在「用户角色」管理中为您分配相应的角色。
+          </p>
+          <Button variant="outline" onClick={logout} className="gap-2">
+            <LogOut className="size-4" />
+            退出登录
+          </Button>
+        </CardContent>
+      </Card>
+    </div>
+  )
+}