Add Korean input and UI translations

[mang0db]

Adds Korean physical keyboard input and Korean UI translations.

Korean input

• Adds the standard Korean two-set (두벌식) layout and a Hangul composer, including compound vowels, final consonant combinations, Shift variants, and keystroke-by-keystroke Backspace.
• Handles composition across spaces, punctuation, cursor and selection changes, editor restarts, and layout switching.
• Centralizes dynamic subtype registration so Korean can be enabled and switched to without a Korean dictionary.

To enable it, select Korean (ko) under Custom Input Styles and choose korean_2set. Korean on-screen keycaps, touch input, and dictionary suggestions are not included.

String localization and Korean translations

• Moves previously hardcoded strings in settings, commands, navigation, and other UI screens into Android string resources. This accounts for much of the change across existing files.
• Adds Korean as an app language, with translations for existing and newly extracted strings.
• Uses the app language for displayed language names and handles regional locale formats consistently, including saved ko_KR settings.
• Adjusts settings rows and navigation labels to accommodate longer translated text.

Testing

• Stable and Nightly debug Kotlin compilation, including Android test sources, passed with OpenJDK 21.
• Each commit passed Stable debug Kotlin compilation.
• All 19 instrumentation tests passed on a Titan 2 Elite (Android 16 / API 36).

[pzauner]

Thanks for your PR. I will for sure look into this and testing it myself.
I can't promise to include it in the one last stable build of Pastiera. But if not it will be included into one of the first Plektra builds.
Expect ~2 weeks for me to look into this huge PR with all the other stuff on board