Finalize React Web App Launch Prep

I already have a fully-functioning React / Vite / Tailwind application deployed on Vercel with Stripe Checkout, webhooks, Supabase, and Resend wired in. The core flows work; now I need everything polished, validated, and ready for public release.

Primary areas of focus
• Email reliability – purchase confirmations, refunds, and email-capture opt-ins must arrive every time, from the correct domain, with Resend running in live mode.
• Data hygiene – Supabase tables should remain clean, typed, and easy to query after each event.
• Tracking – add lightweight, privacy-respecting event tracking (page views, purchase success, refund) so I can verify funnel health.
• UX & compliance – branded cookie banner, legal pages surfaced in the footer, slick ebook delivery via a static replaceable file link, plus domain canonicalisation to avoid duplicate-content issues.
• Technical SEO – sitemap.xml, robots.txt, meta tags, Open Graph, and structured data where relevant.

Acceptance criteria
1. Three complete end-to-end test purchases run in live Stripe, with matching entries in Supabase and the correct emails received.
2. Web, tablet, and mobile performance scores remain green in Lighthouse after your changes.
3. All failure paths (payment declined, email bounce, 404) show helpful messaging and log correctly.
4. Google can fetch the site without warnings, and social share previews pull the intended image and text.

I’ll provide full GitHub access, Stripe keys, Supabase credentials, and Resend sandbox/live tokens. Once everything passes, flip the environment variables to production and push a final build to Vercel.