fix(issues): board card hover uses border color instead of shadow

Dark-mode shadows are invisible — a dark shadow on a dark surface has
almost no contrast. Replace group-hover shadow-md with border-accent so
hover reads in both themes. Hover and active now share the same accent
color (hover = border only; active = border + bg), making active feel
like a natural step up from hover on the same axis.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/views/issues/components/board-card.tsx

@@ -79,7 +79,7 @@ export const BoardCardContent = memo(function BoardCardContent({
   const showChildProgress = storeProperties.childProgress && childProgress;
 
   return (
-    <div className="rounded-lg border-[0.5px] border-border bg-card py-3 px-2.5 shadow-[0_3px_6px_-2px_rgba(0,0,0,0.02),0_1px_1px_0_rgba(0,0,0,0.04)] transition-[border-color,box-shadow,background-color] group-hover/card:shadow-md group-data-[popup-open]/card:border-accent group-data-[popup-open]/card:bg-accent">
+    <div className="rounded-lg border-[0.5px] border-border bg-card py-3 px-2.5 shadow-[0_3px_6px_-2px_rgba(0,0,0,0.02),0_1px_1px_0_rgba(0,0,0,0.04)] transition-[border-color,background-color] group-hover/card:border-accent group-data-[popup-open]/card:border-accent group-data-[popup-open]/card:bg-accent">
       {/* Row 1: Identifier */}
       <p className="text-xs text-muted-foreground">{issue.identifier}</p>