Generate a website called "InvoiceDiff". It should be an SPA and be modern and approachable, but not too "technical". It should accept 2 invoices as a PDF uploads and highlight the differences between them. The actual logic of diffing is handled by an external API, so focus on the front-end only. Follow this structure for the website: [ InvoiceDiff ] Upload left invoice [ PDF ] Upload right invoice [ PDF ] [ Try free demo ] ──────── or ──────── API key: [ __________________ ] [ Compare invoices ] ────────────── Don’t have an API key? [ Get an API key → ]