fix: remove 15 duplicate root-level PDFs, move .env config into next.config.mjs

- Remove duplicate PDFs from repo root (canonical copies remain in pdfs/)
- Move NEXT_PUBLIC_BRAND=hanzo from site/.env into next.config.mjs env block
  to avoid committing env files to git
- Remove site/.env

site/.env

@@ -1 +0,0 @@
-NEXT_PUBLIC_BRAND=hanzo

site/next.config.mjs

@@ -5,6 +5,7 @@ const config = {
   trailingSlash: true,
   basePath: process.env.NEXT_PUBLIC_BASE_PATH || '',
   assetPrefix: process.env.NEXT_PUBLIC_BASE_PATH || '',
+  env: { NEXT_PUBLIC_BRAND: 'hanzo' },
 }
 
 export default config