bug(DIALOG): dialog's container-color does not follow Material 3 design specs

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

As per [Material 3 guidelines](https://m3.material.io/components/dialogs/specs), `container-color` should use value `surface-container-high` token, but it's using value `surface` token.

We can override it by using `dialog-overrides` mixin like below:

```scss
@include mat.dialog-overrides((
container-color: var(--mat-sys-surface-container-high),
));
```

But, it should be the default behaviour as per Material 3 specs.

### Reproduction

Not needed

### Expected Behavior

As per [Material 3 guidelines](https://m3.material.io/components/dialogs/specs), `container-color` should use value `surface-container-high` token.

### Actual Behavior

Dialog's `container-color` is using value `surface` token.

### Environment

- Angular: 19
- CDK/Material: 19
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Windows

No file or test is named. Locate the Angular Material dialog theming implementation and its existing tests, then compare the container-color token with the linked Material 3 dialog specification. Done means the default token uses surface-container-high and the relevant test coverage passes.

Written by the indexing model from the issue text.