Build a modern responsive Sales Tracking Web App for small businesses. Include a dashboard showing Total Sales, Customers, New Enquiries, Follow-ups and Monthly Revenue. Add pages for Customers, Sales, Follow-ups and Reports. Allow users to add customers, record sales, amounts, dates and payment status. Include search, filters, simple charts and a clean professional green/white/dark UI. Make it mobile-friendly and easy for non-technical business owners to use.