Norman: Create Invoice

Help the user create and send an invoice step by step:

1. Identify the client: If a client name is provided in $ARGUMENTS, call list_clients and find the matching client. If ambiguous, ask the user to clarify. If no client exists, offer to create one with create_client.

1. Gather invoice details: Collect the following information (ask for anything not provided):
• Line items: description, quantity, unit price, VAT rate (default 19% for Germany)
• Invoice date (default: today)
• Due date / payment terms (default: 14 days)
• Any notes or special terms

1. Create the invoice: Call create_invoice with all gathered details. Use the correct client_id from step 1.

1. Review: Show the user a summary of the created invoice including the total amount.

1. Send: Ask the user if they want to send the invoice now. If yes, call send_invoice to email it to the client.

Important:

• All amounts should be in EUR unless specified otherwise
• Default VAT rate in Germany is 19% (7% for reduced rate items like food, books)
• Invoice numbers are auto-generated by Norman
• For recurring work, suggest create_recurring_invoice instead