fix(flutter): album/artist card tap (HitTestBehavior.opaque)

Same root cause as the playlist card fix in f65650f — GestureDetector
defers to children by default, so taps over the cover image area
(ServerImage / SVG fallback) didn't reliably propagate. Mark the
detector opaque so the entire card surface is tappable, not just the
text below the cover.

flutter_client/lib/library/widgets/album_card.dart

@@ -14,6 +14,7 @@ class AlbumCard extends StatelessWidget {
   Widget build(BuildContext context) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;
     return GestureDetector(
+      behavior: HitTestBehavior.opaque,
       onTap: onTap,
       child: SizedBox(
         width: 140,

flutter_client/lib/library/widgets/artist_card.dart

@@ -14,6 +14,7 @@ class ArtistCard extends StatelessWidget {
   Widget build(BuildContext context) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;
     return GestureDetector(
+      behavior: HitTestBehavior.opaque,
       onTap: onTap,
       child: SizedBox(
         width: 140,