perf(studio): cache furni imports and virtualize the furniture grid

- Add TTL-based caching for local index lookup, furnidata classnames,
  catalog id set, nitro file presence and import stats
- Invalidate caches after furnace single/batch/clone imports
- Rewrite batch progress with elapsed time, rate and verification chips
- Virtualize the grid with @tanstack/react-virtual and replace the
  Load more button with infinite scroll via an IntersectionObserver

src/app/api/admin/import/furni/batch/route.ts

@@ -19,6 +19,7 @@ import {
 	syncAssetsToGamedataBundle,
 	verifyAndFixInteractionModesCount,
 } from "@/lib/services/furni-import";
+import { clearFurniImportCache } from "@/lib/services/furni-import-cache";
 import { rcon } from "@/lib/services/rcon";
 import type { ImportSingleResult } from "@/types/furni";
 
@@ -195,6 +196,11 @@ export const POST = withAdmin(
 					await new Promise((r) => setImmediate(r));
 				}
 
+				if (succeeded > 0) {
+					// New items + files landed — drop caches so the Studio refresh is fresh.
+					clearFurniImportCache();
+				}
+
 				if (aborted) {
 					send({
 						type: "batch_complete",