displayItemsForPage

Updates the inventory to display items for the current page.

This method clears the existing inventory content, applies the background, and populates the inventory with items specific to the current page. It also sets up navigation buttons if applicable.

The method performs the following actions:

• Clears the inventory and applies a background.

• If there are no items to display, the empty message button is set.

• Items for the current page are added to the inventory based on the defined slot positions.

• Navigation buttons (previous/next) are added if the conditions for navigation are met.

Navigation buttons are only displayed when the respective conditions for their visibility (e.g., not on the first or last page) are met.