fix(website): move v2.alchemy.run redirect into the Worker

[sam-goodwin]

The prod deploy of #806 failed creating the V2Redirect Ruleset — the deploy token has no zone-ruleset permissions:

ERROR: Forbidden: request is not authorized
  at PUT /zones/{zone_id}/rulesets/phases/http_request_dynamic_redirect/entrypoint

Everything else landed: the Worker deployed and both custom domains attached, so alchemy.run is already serving the new site. This PR replaces the Ruleset with a redirect in the Worker itself, which needs no extra token permissions — assets run runWorkerFirst, so the Worker sees every request:

const LEGACY_HOST = "v2.alchemy.run";
const redirectLegacyHost = (request: Request): Response | undefined => {
  const url = new URL(request.url);
  if (url.host !== LEGACY_HOST) return undefined;
  url.host = CANONICAL_HOST;
  return Response.redirect(url.toString(), 301);
};

• The adopted Zone stays declared (adopt + retain).
• The failed Ruleset never created anything, so removing it is a state-only cleanup (no delete API call — its state has no attributes).

If the prod token is later re-minted with zone-ruleset permissions, this can move back to a http_request_dynamic_redirect Ruleset so redirects short-circuit at the edge without invoking the Worker.

🤖 Generated with Claude Code