Standardize error codes and map them to user-friendly messages in the UI

[Aditya8369]

Description: The hook sets setError('WORKER_TIMEOUT') and sometimes sets error to arbitrary messages. The UI prints String(error) directly. This makes it hard to provide consistent, actionable feedback.
Files: lib/hooks/useCipherWorker.ts, components/challenge/ChallengeMode.tsx
Proposed enhancement: Define an error shape or error-code union (e.g., WORKER_TIMEOUT, INVALID_INPUT, WORKER_ERROR) and map to localized UI strings/banners (timeout retry suggestion, validation tips, etc.).

[Aditya8369]

@csxark I would like to work on this issue, please assign me

[github-actions]

🎉 Issue Assigned

Hi @Aditya8369, I'm assigning this initiative to you.

Looking forward to your contributions!

Please do the following before coding:

• ✅ Sync your fork with the latest main
• ✅ Create a new feature branch
• ✅ Implement the requested changes
• ✅ Test your work
• ✅ Open a PR referencing this issue

Wishing you the very best, and happy contributing! 🚀🚀