Simple invoicing for freelancers

Build an invoicing app for a solo freelancer.

Core features:
1. Clients + line items with rate/qty
2. Generate PDF invoice, send by email with pay-online link
3. Stripe hosted payment; mark paid on webhook
4. Dashboard: outstanding, paid this month, YTD
5. Recurring invoices

Data: clients, invoices, line_items, payments.
Must-haves: sequential invoice numbers, tax fields, PDF branded per user.