feat(catalog): store furniture bundles as .hab instead of .nitro

Every bundle the CMS writes — upload, clone, sync, repair and the pet /
effect / figure importers — now lands as `<classname>.hab`, the extension
this deployment's renderer asks for. `.hab` and `.nitro` are the same
container, so an upload of either extension is accepted.

Resolution goes through one module, src/lib/furni/bundle-file.ts, so
nothing has to know the extension twice. Every existence check probes
`.hab` first and falls back to `.nitro`: the on-disk asset set is still
predominantly `.nitro`, and without the fallback Studio would report every
imported item as missing and the cleanup scan would classify 18k live
bundles as fake leftovers. Downloads are unchanged — Habbo's CDN and every
configured clone source still serve `.nitro`, so the conversion happens on
write, not on request.

Deliberately unchanged: the staged-attachment store in furni-attachment.ts
keys on a UUID and never reaches the client, so renaming it would break
in-flight recovery jobs.

Adds scripts/migrate-nitro-to-hab.ts to rename the existing asset set. It
refuses to run without --dry-run or --yes, never overwrites an existing
.hab, never deletes, and is idempotent.

Note: renderer-config.json lives outside this repo and was patched to
.hab separately; that file is served with a 30-day max-age, so returning
clients need a cms-client cache purge to pick the change up.

src/components/admin/studio/furniture-detail-drawer.tsx

@@ -170,7 +170,7 @@ export function FurnitureDetailDrawer({
 							{!detail.nitroExists && (
 								<>
 									<p className="rounded-md border border-[var(--admin-warning)]/30 bg-[var(--admin-warning)]/10 p-2 text-[0.65rem] text-[var(--admin-warning)]">
-										This furni is in the DB but the .nitro file is missing.
+										This furni is in the DB but its bundle file is missing.
 									</p>
 									<Button
 										variant="outline"

src/components/admin/studio/import-attachment-recovery.tsx

@@ -89,13 +89,13 @@ export function ImportAttachmentRecovery({
 		<details className="my-2 rounded border border-[var(--admin-border)] p-2">
 			<summary className="cursor-pointer">{t("recover")}</summary>
 			<p className="my-2 text-xs text-[var(--admin-text-muted)]">
-				{t("recoveryHint", { file: `${classname.split("*")[0]}.nitro` })}
+				{t("recoveryHint", { file: `${classname.split("*")[0]}.hab` })}
 			</p>
 			<label className="block text-xs">
 				{t("attach")}
 				<input
 					type="file"
-					accept=".nitro"
+					accept=".hab,.nitro"
 					className="my-2 block max-w-full"
 					disabled={disabled || busy}
 					onChange={(event) => {

src/components/admin/studio/import-review.tsx

@@ -147,7 +147,7 @@ export function ImportReview({
 							<strong>Source:</strong> {source}
 						</p>
 						<p>
-							<strong>Destination:</strong> local catalog, furnidata, .nitro and
+							<strong>Destination:</strong> local catalog, furnidata, bundle and
 							icons
 						</p>
 						<p>
@@ -349,7 +349,7 @@ export function ImportReview({
 																<input
 																	className="mt-2 block max-w-full"
 																	type="file"
-																	accept=".nitro"
+																	accept=".hab,.nitro"
 																	disabled={busy || uploading !== null}
 																	onChange={(event) => {
 																		const file = event.target.files?.[0];