feat: speed up admin clone import and enable Cache Components

- Clone import: defer FurnitureData.json writes and append all entries in a
  single batched write instead of one read-modify-write per item, removing
  the main serialization bottleneck for large batches.
- Clone import: raise SSE batch concurrency cap from 5 to 10 and bump the
  clone client/route default from 2 to 6.
- Add a flush hook to runSseBatch so callers can batch deferred work before
  batch_complete is emitted, and surface flush errors as an error event.
- Enable Next.js Cache Components (instant: false opt-out) and silence the
  related build warnings in next.config.ts.
- Switch isomorphic-dompurify to dompurify and refresh dependencies.

src/app/(site)/polls/[id]/page.tsx

@@ -13,7 +13,9 @@ import {
 import { formatDate } from "@/lib/format-date";
 import { PollVoteForm } from "./poll-vote-form";
 
-export const dynamic = "force-dynamic";
+// TODO: Cache Components adoption. Refactor this route so this opt-out can be removed.
+// See: https://nextjs.org/docs/app/guides/migrating-to-cache-components
+export const instant = false;
 
 export default async function PollDetailPage({
 	params,

src/app/(site)/polls/page.tsx

@@ -6,7 +6,9 @@ import { db, WebsitePoll, WebsitePollQuestion } from "@/lib/db";
 import { excerpt } from "@/lib/format";
 import { formatDate } from "@/lib/format-date";
 
-export const revalidate = 60;
+// TODO: Cache Components adoption. Refactor this route so this opt-out can be removed.
+// See: https://nextjs.org/docs/app/guides/migrating-to-cache-components
+export const instant = false;
 
 export const metadata = { title: "Polls" };