Invoice Generator

# Invoice Generator PRD

## Overview
Build an invoice generator that lets users create professional invoices with company details, line items, tax and discount calculations, and a print-friendly layout.

## Requirements
- Company details section: name, address, and logo URL
- Client details section: name, address, and email
- Invoice number with auto-increment
- Invoice date and due date fields
- Line items with description, quantity, unit price, and calculated line total
- Add and remove line items dynamically
- Subtotal calculation summing all line items
- Tax rate input with calculated tax amount
- Discount support as percentage or fixed amount
- Grand total with tax and discount applied
- Notes and terms section for payment instructions
- Payment status tracking: unpaid, partial, paid
- Print-friendly layout using CSS @media print
- Multiple currency symbol support
- Save invoices to localStorage
- List all saved invoices with status filter
- Duplicate invoice for a new client
- Responsive design for desktop and mobile

## Tech Stack
- JavaScript or any frontend framework
- CSS for print layout and styling
- No invoice or PDF libraries

## Scoring Criteria
- **Functional (40%)**: Invoice creation works, calculations correct, print layout renders
- **Quality (20%)**: Accurate math, clean professional design, proper form validation
- **Fidelity (25%)**: All features present including status tracking, currency support, and duplicate function
- **Speed (15%)**: Time bonus