/* Shared base shape across the four card components: .articlecard
(cards/article_card.css), .category-card (cards/category_card.css),
.tool-card (cards/tool_card.css), .union-card (cards/union_card.css). Only
declarations that are genuinely byte-for-byte identical across all four are
lifted here -- each card file keeps its own border/border-radius/box-shadow/
color where those actually differ (e.g. .articlecard's border-radius is
3px, .tool-card's is 14px, the other two are 12px; .tool-card's box-shadow
carries an extra glow layer the others don't).

position:relative is deliberately NOT included here even though it looks
like an obvious "card" fundamental: .union-card doesn't set it (it has no
absolutely-positioned descendants of its own, unlike the other three),
so lifting it into this shared rule would silently give .union-card a new
positioning/stacking context it doesn't have today -- exactly the kind of
behavioral change this refactor is meant to avoid. */
.articlecard,
.category-card,
.tool-card,
.union-card {
  box-sizing: border-box;
  overflow: hidden;
  background-color: var(--color-bg);
}