DefaultTemplate FullScreen button with no size after upgrade to next 15

### Describe Your Environment

**What version of Spectacle are you using?**
10.1.8

**What version of React are you using?**
18.3.1

**What browser are you using?**
MS Edge

**What platform are you on?**
macOS

**NextJS version**
15.0.3

### Describe the Problem

By using the DefaultTemplate after upgrading NextJS to v15, the FullScreen button overlays the whole slide with a width of the whole page.

**Expected behavior:**

FullScreen button remains on default size of 24px

**Actual behavior:**

FullScreen button is of size of the page

### Additional Information

Fixed it in my project by copying the DefaultTemplate and modified it, to make it work.

```tsx
type Props = {
color?: string;
iconSize?: number;
};

export const DefaultTemplate = ({ color = '#fff', iconSize = 24 }: Props) => (








);
```

Start by locating the DefaultTemplate and its FullScreen usage, then reproduce the issue with NextJS 15. The work is done when the FullScreen button remains at its default 24px size instead of overlaying the slide, while the progress control still appears correctly.

Written by the indexing model from the issue text.