fix: WalletChip network dropdown transparent background

[marsiandeployer]

Bug

The network selection dropdown in WalletChip (top-right header chip) was rendering with a transparent background, causing page content to show through the menu.

Root Cause

WalletChip/index.scss used var(--color-bg) which is not defined in variables.css. The correct variable is --color-background-elements.

Fix

Changed background: var(--color-bg) → background: var(--color-background-elements) in .dropdown class.