feat(button): add filled/tonal matIconButton

### Feature Description

Currently, matButton supports multiple appearances (text, filled, tonal, outlined, elevated) via the matButton attribute, but matIconButton does not accept any appearance input — it always renders as a transparent circular button.

Material Design 3 specifies [filled and tonal icon button variants](https://m3.material.io/components/icon-buttons/overview) as distinct components alongside the standard and outlined icon buttons. There is currently no straightforward way to create these in Angular Material without using matFab/matMiniFab (which have different sizing, elevation, and semantics) or matButton="filled" with an icon (which doesn't produce a circular icon button).

### Use Case

Developers building M3-compliant UIs need filled and tonal icon buttons for actions that require more visual emphasis than a standard icon button, but don't carry the semantic meaning of a FAB (floating action button). For example, a filled icon button for a primary action like "play" or "add to cart" in a toolbar, or a tonal icon button for a medium-emphasis toggle like "bookmark" or "favorite."

Commencez par comparer les options d’apparence existantes de matButton avec matIconButton, puis examinez les variantes de boutons d’icône de Material Design 3 liées dans l’issue. Le travail est considéré comme terminé lorsque matIconButton peut rendre des apparences remplies et toniques sous forme de boutons d’icône circulaires, distincts des FABs et des boutons d’icône standard.

Rédigé par le modèle d'indexation à partir du texte de l'issue.