Add complete supply chain forecasting educational web app

Built a new from-scratch web application for teaching supply chain forecasting:

Features:
- Data generator: Creates 11 years of realistic monthly sales data for 3 watches
- Historical analysis: Students view 10 years of historical data with charts
- Prediction interface: Input monthly demand forecasts for year 11
- Results evaluation: Compare predictions to actual demand with financial impact
- Performance scoring: Overall score based on accuracy, profit, and service level

The app demonstrates the financial consequences of forecasting errors:
- Under-prediction leads to stockouts and lost revenue
- Over-prediction leads to excess inventory and holding costs

Technologies: Flask, Bulma CSS, Chart.js, NumPy

🤖 Generated with [Claude Code](https://claude.com/claude-code

)

Co-Authored-By: Claude <noreply@anthropic.com>