feat(furniture): add scratching post with simple, tree, condo, wall variants

New SCRATCHING_POST type under a new "pets" category with 8 presets
covering single posts, multi-tier cat trees, enclosed condos, and
wall-mounted scratcher pads. Includes 3D meshes, i18n labels (en/ru),
and palette integration.

packages/shared/src/types/elements.ts

@@ -348,6 +348,7 @@ export const FURNITURE_TYPES = [
   'MIRROR',
   'DIGITAL_PIANO',
   'SPEAKER',
+  'SCRATCHING_POST',
   'OTHER',
 ] as const;
 export type FurnitureType = (typeof FURNITURE_TYPES)[number];