Invoice Manage

When managing invoices:

1. Track — Define invoice data shape in the canvas:
   • Fields: client, amount, status (Draft/Sent/Paid/Overdue), dueDate, createdAt
2. Build canvas — Invoice management section (write_file canvas TSX):
   • KPIs: total outstanding, total paid (30d), overdue count
   • Table: invoices with client, amount, status badge, due date
   • Buttons: Create Invoice, Mark Paid, Send Reminder (handled as local state in canvas)
3. Create — When user asks to create an invoice:
   • Parse client, amount, and due date from natural language
   • Add the new row to the canvas data and re-write the file
4. Follow up — On heartbeat, check for overdue invoices:
   • Alert via send_message if any invoices are past due
   • Log overdue status to memory
5. Report — Weekly summary of cash flow (paid vs outstanding)