PayrocDSpatz/farrier-pro ? reverse-engineered prompt

Build me a polished web app for FarriTech that handles sign up, login, and a simple customer portal.

I want a landing page, a mobile friendly view, a bulk upload page, and a customer portal page, all tied together with Firebase sign in. Signup should be smooth and rely on Firebase auth errors to tell people if their email is already used, instead of doing a separate email check. The app should also support subscription setup through Authorize.net, with a trial period if that is available, and a serverless API route for creating subscriptions.

Please make it feel clean and professional, with a working auth flow, an OAuth callback page, and the basic pages wired up so a user can actually move through the app without dead ends. If you need to check current Firebase or Authorize.net details, look up the latest docs online.