♻️ refactor(admin): add default export for MembershipPlans component

- export default MembershipPlans to support default import syntax
- improve module import consistency across the application

src/client/admin/pages/MembershipPlans.tsx

@@ -777,4 +777,6 @@ export const MembershipPlans = () => {
       </Dialog>
     </div>
   );
-};
+};
+
+export default MembershipPlans;