我找到了解决办法。不知道这是否是最好的方法，但它在这里。
我创建了一个客户端组件来检查某人是否是管理员：

components/dashboard/AdminComponent.tsx

此解决方案不起作用。我敢打赌，我使用useEffect的错误，不知何故，可以修复，但下面的替代解决方案工作正常。

"use client"

import React from "react"
import { redirect } from "next/navigation"
import ky, { KyResponse } from "ky"

import { BASE_URL } from "@/app/lib/constants"

export const AdminComponent = () => {
    const [admin, setAdmin] = React.useState(false)

    React.useEffect(() => {
        const fetchAdmin = async () => {
            const res: KyResponse & { isAdmin: boolean } = await ky.get(`${BASE_URL}/api/admin`).json()
            setAdmin(res.isAdmin)
        }
        fetchAdmin()
    }, [])

    if (!admin) redirect("/dashboard")

    return null
}

然后，我将客户端组件导入到服务器组件中。

pages/admin.tsx

import React from "react"
import { redirect } from "next/navigation"

import { getPageSession } from "@/app/auth/lucia"
import { AdminComponent } from "@/app/components/dashboard/AdminComponent"

const Admin = async () => {
    const session = await getPageSession()

    if (!session) redirect("/login")

    return (
        <div className="isolate bg-slate-900 text-white">
            ...
        </div>
    )
}

export default Admin

我还将AdminComponent重写为：

"use client"

import React from "react"
import { redirect } from "next/navigation"
import ky, { KyResponse } from "ky"

import { BASE_URL } from "@/app/lib/constants"

const fetchAdmin = React.cache(async () => {
    const res: KyResponse & { isAdmin: boolean } = await ky.get(`${BASE_URL}/api/admin`).json()
    return res.isAdmin
})

export const AdminComponent = () => {
    const admin = React.use(fetchAdmin())

    if (!admin) redirect("/dashboard")

    return null
}

这看起来干净得多，但到目前为止还不是一个常见的模式。
想知道是否有更简单或更干净的解决方案。

编辑：

找到了更好的解决办法。

components/dashboard/AdminComponent.tsx

"use client"

import React from "react"
import { redirect } from "next/navigation"

import { useAdminStatus } from "@/app/hooks/useAdminStatus"

// eslint-disable-next-line react/display-name
export const AdminComponent = React.memo(() => {
    const { data, error, isLoading } = useAdminStatus()

    if (isLoading) return null
    if (error) return <span className="text-slate-500">Failed to load `AdminComponent`</span>

    if (!data.isAdmin) redirect("/dashboard")

    return null
})

hooks/useAdminStatus.tsx

import useSWRImmutable from "swr/immutable"

const fetcher = (...args: [any]) => fetch(...args).then((res) => res.json())

export const useAdminStatus = () => {
    const { data, error, isLoading } = useSWRImmutable(`/api/admin`, fetcher)

    return {
        data,
        error,
        isLoading,
    }
}