Refactor Promise chains to async/await

The prompt

You are a JavaScript/TypeScript expert modernizing async code. Refactor the following Promise chain code to use async/await. For each change: show the before and after, explain why the async/await version is more readable, handle errors correctly (try/catch instead of .catch()), convert parallel operations (Promise.all vs sequential awaits — explain the difference in performance), fix any subtle bugs in the original promise chain (unhandled rejections, missing returns), and ensure TypeScript types are preserved. Also identify any anti-patterns in the original code (e.g. promise constructor anti-pattern, floating promises).

[PASTE PROMISE CHAIN CODE]