feat(styles,react): use button and button card as links

[Gnuk]

What

Allow button and button-card to be used as links (<a href>) without underline, in both the Pattern Library and the React components.

Pattern Library (@ippon-ui/styles 0.0.8)

• text-decoration: none on .ippon-button and .ippon-button-card
• ippon-button and ippon-button-card Pug mixins accept an href option and render an <a> instead of a <button> (same convention as the tab atom)
• Link examples added to both component docs, render heights adjusted so nothing is cut off

React (@ippon-ui/react 0.0.7)

• New IpponLinkButton and IpponLinkButtonCard components: link (<a href>) counterparts of IpponButton and IpponButtonCard, sharing their look but exposing only link-relevant props (href required; no disabled, loading or popover behavior, which only make sense on real buttons)
• Shared button types and icon rendering extracted to Button.tsx, consumed by both IpponButton and IpponLinkButton
• Dedicated Storybook stories (Atom/LinkButton, Organism/LinkButtonCard), README example, dedicated specs (256 tests passing)
• Peer dependency raised to @ippon-ui/styles ~0.0.8 (link rendering relies on the new underline reset)

Notes

• CHANGELOG entry added for both packages
• The [unplugin:dts] api-extractor build warning is pre-existing and unrelated

🤖 Generated with Claude Code