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/lib/furni/classname.ts

@@ -17,8 +17,39 @@ export function getSwfFileName(classname: string): string {
 	return `${getBaseClassname(classname)}.swf`;
 }
 
+/**
+ * Extension locally stored furniture bundles are written with. This deployment's
+ * Nitro client requests `<classname>.hab`, so that is what new imports produce.
+ */
+export const LOCAL_BUNDLE_EXT = ".hab";
+
+/**
+ * Extension remote sources serve bundles with. Upstream (Habbo's CDN and every
+ * configured clone source) keeps shipping `.nitro`, so download URLs are built
+ * with this and only re-written to `LOCAL_BUNDLE_EXT` once they land on disk.
+ */
+export const SOURCE_BUNDLE_EXT = ".nitro";
+
+/** Both extensions a local bundle may carry, newest convention first. */
+export const LOCAL_BUNDLE_EXTS = [LOCAL_BUNDLE_EXT, SOURCE_BUNDLE_EXT] as const;
+
+/** Primary local bundle name — `.hab` wins over a legacy `.nitro`. */
 export function getNitroFileName(classname: string): string {
-	return `${getBaseClassname(classname)}.nitro`;
+	return `${getBaseClassname(classname)}${LOCAL_BUNDLE_EXT}`;
+}
+
+/** Every local file name this classname's bundle may be stored under. */
+export function getLocalBundleFileNames(classname: string): string[] {
+	const base = getBaseClassname(classname);
+	return LOCAL_BUNDLE_EXTS.map((ext) => `${base}${ext}`);
+}
+
+/** File name for an explicit extension — use `SOURCE_BUNDLE_EXT` for URLs. */
+export function getBundleFileName(
+	classname: string,
+	ext: string = LOCAL_BUNDLE_EXT,
+): string {
+	return `${getBaseClassname(classname)}${ext}`;
 }
 
 export function normalizeClassname(raw: string): string {