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/api/tickets/[id]/reply/route.ts

@@ -15,8 +15,6 @@ import {
 import { rateLimit } from "@/lib/rate-limit";
 import { createOwnedTicketReply } from "@/lib/services/ticket-replies";
 
-export const dynamic = "force-dynamic";
-
 // POST /api/tickets/:id/reply  body: { content }
 export async function POST(
 	req: Request,

src/app/api/tickets/[id]/route.ts

@@ -14,8 +14,6 @@ import {
 	WebsiteHelpCenterTickets,
 } from "@/lib/db";
 
-export const dynamic = "force-dynamic";
-
 // GET /api/tickets/:id
 export async function GET(
 	req: Request,

src/app/api/tickets/route.ts

@@ -11,8 +11,6 @@ import { bearerUserId } from "@/lib/api-auth";
 import { db, WebsiteHelpCenterTickets } from "@/lib/db";
 import { rateLimit } from "@/lib/rate-limit";
 
-export const dynamic = "force-dynamic";
-
 // GET /api/tickets — the authed user's tickets (newest first).
 export async function GET(req: Request) {
 	const uid = await bearerUserId(req);