refactor: replace Toast with Sonner

frontend/app/routes/system-users.tsx

@@ -1,6 +1,6 @@
 import { useAuth } from "~/context/AuthContext";
 import { useScriptWorkspaceStore } from "~/features/platform/state/scriptWorkspaceStore";
-import { useUiStore } from "~/features/platform/state/uiStore";
+import { toast } from "sonner";
 import { UserManagementPage } from "~/features/admin/UserManagementPage";
 
 /**
@@ -11,7 +11,11 @@ import { UserManagementPage } from "~/features/admin/UserManagementPage";
 export default function UserManagementRoute() {
   const { user, currentWorkspace } = useAuth();
   const setApiOnline = useScriptWorkspaceStore((s) => s.setApiOnline);
-  const pushToast = useUiStore((s) => s.pushToast);
+  const pushToast = (notice: { tone: "success" | "error" | "info"; message: string }) => {
+    if (notice.tone === "error") toast.error(notice.message);
+    else if (notice.tone === "info") toast.info(notice.message);
+    else toast.success(notice.message);
+  };
 
   return (
     <UserManagementPage