feat(preview): Add interactive PopoverButton preview component

[Copilot]

Adds an interactive preview for the PopoverButton component, replacing the static HTML code snippet and commented-out Live-Editor/Configurator placeholders in both German and English docs.

Changes

• src/components/previews/components/PopoverButton.tsx — new slot-based preview component exposing _label, _popoverAlign, _variant, _icons, _slot, _disabled, _hideLabel; slot content sanitized via sanitizeHtml
• i18n/de/code.json + i18n/en/code.json — adds preview.component.popover-button.label and preview.component.popover-button.slot translation keys
• docs/30-components/popover-button.mdx + i18n/en/.../popover-button.mdx — swaps static example and dead comments for <PopoverButtonPreview>, removes tags: frontmatter section, restructures # API heading

<PopoverButtonPreview
  visibleProperties={['_label', '_popoverAlign', '_icons', '_slot', '_disabled', '_hideLabel']}
  codeCollapsable
  codeCollapsed
/>

[github-actions]

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