bug: Accept-Language: pl not recognized by Logto Cloud language detection

[Green7]

Describe the bug

I've noticed that Logto Cloud's automatic language detection does not recognize pl (Polish) as a valid language for the UI.

How to reproduce?

Using the Accept-Language header in the browser:

es → UI appears in Spanish ✅

pl-PL → UI appears in Polish ✅

pl → UI falls back to English ❌

This is inconsistent, as pl is a valid and commonly used language code. Most systems treat pl and pl-PL as equivalent or fallback-compatible.

[darcyYe]

Thank you for reporting this, the team will take a look.