Feature Request: Add Category and Items for POS System (Currently Category & Items are static)

# 📌 Add Category and Items for POS System

## Description
We need to implement a feature where users can **add categories** (e.g., Beverages, Snacks, Main Course) and **items** under each category in the POS system. This will help in organizing products and improving the user experience.

## 🎯 Expected Features
### Category Management:
- Add a new category
- Edit & delete an existing category
- Display all categories

### Item Management:
- Add an item under a selected category
- Edit & delete an item
- Display all items under respective categories

## 🛠️ Tech Stack & Requirements
- **Frontend:** React with Redux for state management
- **Backend:** Node.js with Express and MongoDB/PostgreSQL

### API Endpoints:
- `POST /categories` – Create a new category
- `GET /categories` – Fetch all categories
- `PUT /categories/:id` – Update a category
- `DELETE /categories/:id` – Delete a category
- `POST /items` – Create an item under a category
- `GET /items?categoryId=xyz` – Fetch items by category
- `PUT /items/:id` – Update an item
- `DELETE /items/:id` – Delete an item

## ✅ Tasks
- [ ] Create UI components for category & item management
- [ ] Implement Redux actions and reducers
- [ ] Develop API routes in the backend
- [ ] Connect frontend with API
- [ ] Test the functionality

## 💡 Additional Notes
- Make sure to handle error validation.
- Feel free to suggest any improvements or additional features!

🚀 **Want to contribute?** Comment below or create a pull request!