Migrate deployment to Cloudflare Pages

[jglopez]

Currently deployed via the built-in Pages workflow. To migrate:

1. Swap actions/upload-pages-artifact + actions/deploy-pages in deploy.yml for cloudflare/pages-action
2. Remove or env-var the base path in vite.config.ts — currently set to the repo name, which only applies when serving from a subpath. A custom domain or Cloudflare Pages root deployment doesn't need it.

No code changes needed beyond those two steps.