fix: use dedicated article-card partial for taxonomy pages

fix: use dedicated article-card partial for taxonomy pages

The timeline partial (article-list-item.html) always emits <li> with
timeline connector and node markup — calling it with . still produces
the same timeline HTML. Created article-card.html with the original
<article class="card"> markup and wired taxonomy templates to use it.

Co-Authored-By: Claude Haiku 4.5 <redacted>