feat(cloudflare/ratelimit): add RateLimit binding

[agcty]

Adds a Cloudflare RateLimit marker and binding policy so Workers can attach type: "ratelimit" metadata via direct bindings or init-phase RateLimit.bind.

const signupThrottle = yield* Cloudflare.RateLimit({
  namespaceId: 1001,
  simple: { limit: 10, period: 60 },
});

export const Worker = Cloudflare.Worker("Worker", {
  main: "./src/worker.ts",
  bindings: { SIGNUP_THROTTLE: signupThrottle },
});

Depends on alchemy-run/distilled#256 for generated Workers upload schema support.

[agcty]

Verification update:

• Focused binding tests passed: bun vitest run packages/alchemy/test/Cloudflare/RateLimit/RateLimit.test.ts
• This PR depends on the Distilled upload schema fix in fix(cloudflare/workers): support ratelimit upload bindings distilled#256 for Worker script uploads containing ratelimit bindings.