Fix React error #130 by correcting Card component usage

- Fixed all Card components to use padding prop instead of className
- Updated padding values: p-4 -> sm, p-6 -> md, p-8 -> lg
- This resolves the React element type invalid error

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

frontend/src/pages/admin/EventsListPage.tsx

@@ -169,7 +169,7 @@ export const EventsListPage: React.FC = () => {
         </div>
 
       {/* Filters and Search */}
-      <Card className="p-4 mb-6">
+      <Card padding="sm" className="mb-6">
         <div className="flex flex-col lg:flex-row gap-4">
           {/* Search */}
           <div className="flex-1">