Recipe Scaler

# Recipe Scaler PRD

## Overview
Build a recipe scaling application that parses ingredient quantities and dynamically adjusts them based on desired servings, with support for fractions, unit conversion, and shopping lists.

## Requirements
- Input recipe name and a list of ingredients with quantities
- Parse ingredient quantities in various formats (1 cup, 2.5 tbsp, 1/3 tsp, 3 cloves)
- Input for original number of servings
- Scale ingredients by entering a desired number of servings
- Slider for quick scaling from 0.5x to 5x the original recipe
- Display fractions properly in output (show 1/3 instead of 0.333)
- Unit conversion toggle between metric and imperial measurements
- Save recipes to localStorage with timestamps
- Edit and update previously saved recipes
- Shopping list mode: combine ingredients from multiple selected recipes
- Print-friendly layout with clean formatting for printing
- Share recipe as copyable plain text
- Categorize recipes (breakfast, lunch, dinner, dessert, snack)
- Search saved recipes by name or ingredient

## Tech Stack
- HTML, CSS, JavaScript (vanilla or any framework)
- No recipe or measurement libraries — parse and convert units yourself

## Scoring Criteria
- **Functional (40%)**: Ingredient parsing works, scaling calculates correctly, fractions display properly
- **Quality (20%)**: Handles edge cases (zero servings, unusual units), clean code
- **Fidelity (25%)**: All features present including shopping list, print layout, search
- **Speed (15%)**: Time bonus