Fix shop room preview showing solid green LCD background.

Include lib/ in Tailwind content so parallax room gradient classes from room-backgrounds.ts are emitted in production CSS.

lib/shop-preview.ts

@@ -1,6 +1,21 @@
 import type { AvatarCustomization } from "@/lib/avatar-customization-storage";
 import { parseVariantId, parseShopStyleItem, type ShopItemRecord } from "@/lib/shop-catalog";
-import { normalizeRoomBackgroundId } from "@/lib/room-backgrounds";
+import {
+  normalizeRoomBackgroundId,
+  type RoomBackgroundId,
+} from "@/lib/room-backgrounds";
+
+/** Room id shown behind the pet in shop preview (shop item id, not image_path). */
+export function getShopPreviewRoomId(
+  item: ShopItemRecord,
+  base: AvatarCustomization,
+): RoomBackgroundId {
+  if (item.type === "room") {
+    return normalizeRoomBackgroundId(item.id);
+  }
+
+  return normalizeRoomBackgroundId(base.roomBackground);
+}
 
 /** Build a non-persisted avatar state showing how a shop item would look. */
 export function buildShopItemPreviewCustomization(