Live Flight Fare Tracker – Instant Price Drop Alerts via SMS & Email

### 🔍 Fare Comparison & Alert Logic

1.  **Code**: This critical node compares the `current_fare` from the "Process Flight Data" node with the `previous_fare` fetched from "Google Sheets". It calculates fare changes (absolute and percentage) and determines if an alert is needed based on predefined thresholds (e.g., >=10% drop or >=15% increase).
2.  **Check if Alert Needed**: An If node that checks if the `fare_change` calculated in the Code node is non-zero. If there's a change, it proceeds to format and send alerts.