Add all-in-one Studio merging furni import and catalog management

Add a full-viewport /admin/studio workspace that unifies the import and
catalog systems into a single automated flow:

- Furni library browser against official Habbo furnidata with search,
  type/status filters, live previews and pagination
- Catalog structure rail showing where imported furniture lands
- Detail drawer with automatic placement preview (category + price via
  classifyFurni/autoPriceFurni) and one-click import that downloads
  assets, converts SWF to nitro, writes items_base, updates
  FurnitureData.json and creates an auto-priced catalog entry
- Batch auto-import with SSE progress and RCON cache refresh
- Nitro editor integration and imported-item deletion

Extract pure auto-catalog helpers (CATEGORY_PAGE, CLASSNAME_RULES,
classifyFurni, autoPriceFurni) into a client-safe module shared by the
server pipeline and the Studio UI so the preview always matches what the
emulator import applies.

src/lib/admin-nav.ts

@@ -23,6 +23,7 @@ import {
 	Monitor,
 	Newspaper,
 	Package,
+	Palette,
 	Radio,
 	Server,
 	Settings,
@@ -622,6 +623,13 @@ export const ADMIN_NAV_GROUPS: AdminNavGroup[] = [
 				permission: PERMS.ROOMS_VIEW,
 				matchPrefixes: ["/admin/rooms"],
 			},
+			{
+				href: "/admin/studio",
+				labelKey: "studio",
+				icon: Palette,
+				permission: PERMS.ASSETS_IMPORT,
+				matchPrefixes: ["/admin/studio"],
+			},
 			{
 				href: "/admin/import",
 				labelKey: "import",