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/sitemap.ts

@@ -4,7 +4,6 @@ import { db, Guilds, WebsiteArticles } from "@/lib/db";
 
 // Built at request time — avoids competing with SSG workers for scarce DB
 // connections during `next build` (pool timeouts killed deploy on sitemap).
-export const dynamic = "force-dynamic";
 
 export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
 	const appUrl = process.env.APP_URL ?? "http://localhost:3000";