Refactor backlog component to use single state object

Reorganized the backlog component to consolidate multiple useState calls into one single state object. This change offers a cleaner approach for managing state in this component, fosters readability, and can potentially improve performance by reducing the number of re-rendering triggers. The interface used for the showModal prop has also been updated to accommodate this change.

frontend/components/Backlog/Modal/modal.type.ts

@@ -3,6 +3,8 @@ import { Dispatch, SetStateAction } from 'react';
 export default interface ModalProps {
   children: React.ReactNode;
   showModal: boolean;
-  setShowModal: Dispatch<SetStateAction<boolean>>;
+  setShowModal:
+    | Dispatch<SetStateAction<boolean>>
+    | ((showModal: boolean) => void);
   containerClasses?: string;
 }