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/services/pet-icon.ts

@@ -1,4 +1,5 @@
-import { existsSync, readFileSync } from "node:fs";
+import { readFileSync } from "node:fs";
+import { resolveBundleInDir } from "@/lib/furni/bundle-file";
 import { cropRgba, decodePng } from "@/lib/services/imager/png-decode";
 import { encodePng, parseNitroBundle } from "@/lib/services/swf/nitro-builder";
 import { getRuntimePath } from "@/lib/utils/runtime-path";
@@ -54,8 +55,8 @@ const iconCache = new Map<string, Buffer | null>();
 
 function findNitro(lib: string): string | null {
 	for (const dir of PET_DIRS) {
-		const p = getRuntimePath(/*turbopackIgnore: true*/ dir, `${lib}.nitro`);
-		if (existsSync(/*turbopackIgnore: true*/ p)) return p;
+		const p = resolveBundleInDir(/*turbopackIgnore: true*/ dir, lib);
+		if (p) return p;
 	}
 	return null;
 }