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/admin/translations/client/page.tsx

@@ -7,6 +7,10 @@ import {
 } from "@/lib/client-translation-files";
 import { ClientTranslations } from "./client-translations";
 
+// 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 ClientTranslationsPage({
 	searchParams,
 }: {

src/app/admin/translations/cms/page.tsx

@@ -2,6 +2,10 @@ import fs from "node:fs/promises";
 import path from "node:path";
 import { TranslationsClient } from "../translations-client";
 
+// 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;
+
 const LOCALES = [
 	"en",
 	"it",

src/app/admin/translations/emulator/page.tsx

@@ -7,6 +7,10 @@ import { Button } from "@/components/ui/button";
 import { calcPagination } from "@/lib/admin-helpers";
 import { db, EmulatorSettings } from "@/lib/db";
 
+// 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;
+
 const TRANSLATION_KEY_PATTERNS = [
 	"commands.description.",
 	"commands.keys.",

src/app/admin/translations/layout.tsx

@@ -2,6 +2,10 @@ import { redirect } from "next/navigation";
 import { canAccess, getAdminContext, PERMS } from "@/lib/permissions";
 import { TranslationsTabs } from "./translations-tabs";
 
+// 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 TranslationsLayout({
 	children,
 }: {

src/app/admin/translations/page.tsx

@@ -1,5 +1,9 @@
 import { redirect } from "next/navigation";
 
+// 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;
+
 // Default landing for /admin/translations → first tab.
 // The shared TranslationsTabs (in layout.tsx) gives access to every section.
 export default function TranslationsHubPage() {