Adds functionality to process and display advertising data alongside sales data. This includes:
- Introducing a new `AdvertisingDashboard` component.
- Modifying `FileUpload` to accept advertising CSVs.
- Updating `App.tsx` to manage and display both sales and ad data.
- Enhancing `dataProcessor.ts` to handle advertising CSV parsing and merging.
- Adding a `MegaphoneIcon` for advertising-related UI elements.
- Defining new types for advertising records and combined KPIs.
