Refactor modal implementation across admin components: Replace Card components with a reusable Modal component in ChallengeManagement, EventManagement, and UserManagement, enhancing UI consistency and maintainability. Update Modal to use React portals for improved rendering.

components/ui/Modal.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import { ReactNode, useEffect } from "react";
+import { createPortal } from "react-dom";
 
 interface ModalProps {
   isOpen: boolean;
@@ -37,7 +38,7 @@ export default function Modal({
 
   if (!isOpen) return null;
 
-  return (
+  const modalContent = (
     <div
       className="fixed inset-0 z-[200] flex items-center justify-center p-4 backdrop-blur-sm"
       style={{
@@ -59,4 +60,11 @@ export default function Modal({
       </div>
     </div>
   );
+
+  // Utiliser un portal pour rendre le modal directement dans le body
+  if (typeof window !== "undefined") {
+    return createPortal(modalContent, document.body);
+  }
+
+  return null;
 }