chore: import upstream snapshot with attribution

apps/webapp/app/routes/resources.platform-notifications.$id.seen.tsx

@@ -0,0 +1,17 @@
+import { json } from "@remix-run/node";
+import type { ActionFunctionArgs } from "@remix-run/node";
+import { requireUserId } from "~/services/session.server";
+import { recordNotificationSeen } from "~/services/platformNotifications.server";
+
+export async function action({ request, params }: ActionFunctionArgs) {
+  const userId = await requireUserId(request);
+  const notificationId = params.id;
+
+  if (!notificationId) {
+    return json({ success: false }, { status: 400 });
+  }
+
+  await recordNotificationSeen({ notificationId, userId });
+
+  return json({ success: true });
+}