Add notification variables

[adrianspdev]

Note

Low Risk
Low risk: adds new theme token keys and a CSS selector mapping for the notification close icon without changing existing behavior or logic.

Overview
Adds a new set of theme token keys for notification/toast styling (foreground/background/border plus success/warning/error accent colors).

Updates iconsMap to render a close icon for notifications by mapping .ht-notification__close::before to the existing chipClose asset.

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