feat(www): deploy site to Cloudflare with Alchemy

Add an Alchemy stack that builds the Astro site and serves dist/ from
the www Worker (www.codeworksh.workers.dev), plus the www-bucket-<stage>
R2 bucket. `pnpm run deploy` deploys the live stage.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: sanchitrk

.gitignore

@@ -53,3 +53,5 @@ temp
 models.json
 models.gen.json
 .astro
+
+.alchemy