feat: Add Chinese (zh_CN) localization support

[a00331111]

Hi! I'd like to contribute Chinese (Simplified) localization to this project.

I noticed all UI strings are currently hardcoded in English. Adding i18n support would make this useful tool accessible to more users.

Before I start working on a PR, I wanted to check:

1. Are you open to localization contributions?
2. Do you have any preferred approach ( files vs )?
3. Any specific guidelines for translations?

Here's what I'm planning:

• Create directory
• Extract all UI strings to localization files
• Add Chinese translations

Let me know if this sounds good, and I'll get started! 🚀