feat: implement Portal component and refactor modals to use it for improved positioning

assets/admin/components/ui/InviteDoctorModal.tsx

@@ -7,6 +7,7 @@ import { toast } from 'sonner';
 import { api } from '../../lib/api';
 import type { ApiResponse } from '../../lib/api';
 import MobileInput from './MobileInput';
+import Portal from './Portal';
 import { iranMobileSchema } from '../../lib/utils';
 
 const inviteSchema = z.object({
@@ -39,6 +40,7 @@ export default function InviteDoctorModal({ clinicUuid, onClose, onInvited }: Pr
   });
 
   return (
+    <Portal>
     <div className="overlay" onClick={onClose}>
       <div className="modal" style={{ maxWidth: 420 }} onClick={e => e.stopPropagation()}>
         <div className="modal-head">
@@ -71,5 +73,6 @@ export default function InviteDoctorModal({ clinicUuid, onClose, onInvited }: Pr
         </form>
       </div>
     </div>
+    </Portal>
   );
 }