Static single-page invoice app per spec. Features:
- Multilingual UI (EN/DE/FR/NO) loaded from config.yml; form always
prints in the default language
- Sender fields + invoice details (date, project code, invoice no.)
persisted in localStorage; invoice number auto-increments after
each generation
- Predefined charge-to recipients selectable from config, or manual entry
- Dynamic invoice line items: predefined products with UOM/price
pre-fill, free-text fallback, foreign-currency sub-row with
exchange-rate and per-item price that calculates back to local currency
- Subtotal / tax (configurable rates) / paid / to-pay calculated live
- "Generate Invoice" renders a clean A4-formatted preview overlay;
"Print / Save as PDF" triggers browser print-to-PDF
https://claude.ai/code/session_015iyCBgoTXNNqaErR287U1u
