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/users/[username]/route.ts

@@ -9,8 +9,6 @@ import { eq } from "drizzle-orm";
 import { apiJson } from "@/lib/api";
 import { db, User } from "@/lib/db";
 
-export const dynamic = "force-dynamic";
-
 export async function GET(
 	_req: Request,
 	{ params }: { params: Promise<{ username: string }> },