test: expose notification card state for browser coverage

Author: stefan-ernst

frontend/src/lib/features/notifications/NotificationCard.svelte

@@ -60,6 +60,8 @@
 </script>
 
 <div
+  data-testid={`notification-card-${notification.id}`}
+  data-read={notification.read}
   class="notification-card p-4 cursor-pointer transition-colors relative group"
   class:unread={!notification.read}
   style="border-bottom: 1px solid var(--ds-border);"
@@ -145,4 +147,4 @@
     -webkit-box-orient: vertical;
     overflow: hidden;
   }
-</style>
+</style>