fix: resolve all TypeScript errors in web app

apps/web/src/components/widgets/BaseWidget.tsx

@@ -5,7 +5,11 @@
 
 import type { ReactNode } from "react";
 import { Settings, X } from "lucide-react";
-import { cn } from "@mosaic/ui/lib/utils";
+
+// Simple classnames utility
+function cn(...classes: (string | undefined | null | false)[]): string {
+  return classes.filter(Boolean).join(" ");
+}
 
 export interface BaseWidgetProps {
   id: string;