feat(BBBToast): add notification card component

[Arthurk12]

What does this PR do?

Add BBBToast, the presentational card for transient notifications: an icon badge matched to variant, a title row it shares with the close button, and a content area below, both aligned to the same edge.

The card never hides itself. The close button and the autoClose timer both call onRequestClose, leaving removal to whoever owns the toast stack, so the card can sit inside an external engine without leaving an empty slot behind. maxHeight caps it and scrolls its body past that point, since those engines clip their own containers with no scrollbar. The card fills the width of the slot it is given, since engines wrap each toast in a flex container that would otherwise shrink it to its content and leave a stack of mismatched widths, and its body keeps room for the close button's focus ring, which the scroll container would otherwise clip.

The autoClose countdown pauses while the card is hovered or has focus inside it, and resumes with the time left, so the toast does not vanish under someone reading it or about to press one of its buttons (WCAG 2.2.1, Timing Adjustable). A bar along the bottom of the card counts the delay down and pauses with it, showing how long the toast has left; hideProgressBar drops it. paused holds both from outside, for engines that pause a whole stack while it is hovered, since the card only sees the pointer over itself.

Every badge carries a white glyph. White fails the 3:1 non-text contrast (WCAG 1.4.11) on the palette's success and warning fills (1.97:1 and 2.32:1), so those badges use new darker shades, colorSuccessDark and colorWarningDark (about 3.6:1), exposed as --color-success-dark and --color-warning-dark so themes can override them. A dark glyph passes too, but it set those two variants apart from the rest.

The card is a live region, which rules out role="button" on it, and it holds buttons of its own, so a clickable container would nest interactive elements and swallow their Enter/Space presses. With onClick, the click is exposed through a real button wrapping message instead: it is announced as a button, reachable with Tab and activated natively, and its focus ring outlines the whole card. clickAriaLabel names it when the message does not describe the action, and clicks on interactive elements passed in message or content stay with those elements. The pointer cursor follows onClick by default, with disablePointer as an override.

The close button takes closeButtonAriaLabel, since a hardcoded English name is what screen readers announce in every locale. The live-region attributes stay overridable through the rest props, for engines whose wrapper is already a live region, while the card's own handlers and test id are applied after them.

Prop names follow the library rather than react-toastify or BBB's notify(): variant as in BBButton and BBBTypography, and hideCloseButton as in BBBHint, so opting out of the close button reads the same across components. DOM-driven handlers (onClick, onActionClick) receive the event, as in BBButton; onRequestClose does not, as in BBBHint, since the timer fires it too. small keeps its name to match the field already in BBB's notify() and in the plugin SDK.

message is optional, for cards whose content reads on its own, and typed as a node rather than a string because four call sites pass a <FormattedMessage> that cannot be flattened without losing inline markup.

Closes Issue(s)

Closes #72