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 <noreply@anthropic.com>

frontend/src/pages/admin/CreateEventPage.tsx

@@ -170,7 +170,7 @@ export const CreateEventPage: React.FC = () => {
 
       <form onSubmit={handleSubmit}>
         {/* Event Details */}
-        <Card className="p-6 mb-6">
+        <Card padding="md" className="mb-6">
           <h2 className="text-lg font-semibold text-neutral-900 mb-4">Event Details</h2>
           
           <div className="space-y-4">
@@ -246,7 +246,7 @@ export const CreateEventPage: React.FC = () => {
         </Card>
 
         {/* Contact Information */}
-        <Card className="p-6 mb-6">
+        <Card padding="md" className="mb-6">
           <h2 className="text-lg font-semibold text-neutral-900 mb-4">Contact Information</h2>
           
           <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
@@ -291,7 +291,7 @@ export const CreateEventPage: React.FC = () => {
         </Card>
 
         {/* Security & Access */}
-        <Card className="p-6 mb-6">
+        <Card padding="md" className="mb-6">
           <h2 className="text-lg font-semibold text-neutral-900 mb-4">Security & Access</h2>
           
           <div className="grid grid-cols-1 md:grid-cols-2 gap-4">
@@ -344,7 +344,7 @@ export const CreateEventPage: React.FC = () => {
         </Card>
 
         {/* Gallery Settings */}
-        <Card className="p-6 mb-6">
+        <Card padding="md" className="mb-6">
           <h2 className="text-lg font-semibold text-neutral-900 mb-4">Gallery Settings</h2>
           
           <div className="space-y-4">