IAP Manager

1. purchasableItems (Type: IAPItem[]) List of IAP items that can be purchased. Each IAPItem is a ScriptableObject that defines a product available for purchase within the game.

2. purchaseMode (Type: PurchaseMode) Sets whether the game runs in Test Mode or Production Mode. In Test Mode, purchases are simulated without processing real transactions; in Production Mode, real purchases are handled via the app stores.