Support Per-app language preferences

[314systems]

Summary

• Support Per-app language preferences

What does this implement/fix?

• Support Per-app language preferences.

Does this close any issues?

• Closes [Feature] Support Per-app language preferences #577

How was this tested?

• Devices / OS (e.g. Android 13 emulator, Pixel 6):
• Platform / Build variant (e.g. debug/release):
• Toolchain / Gradle / SDK version(s):
• Steps to reproduce / test (provide exact steps so reviewers can verify):

Example test commands:

./gradlew ktlintCheck

Checklist (required before marking ready)

• I added or updated unit tests (see app/src/test/)
• I followed the project's coding style (ktlint) and formatting
• I ran lint and addressed or documented any warnings
• CI checks pass (unit tests, coverage, lint)
• No sensitive data, keys, or secrets are included

Additional context

• Screenshots, logs, or other context that helps reviewers understand the change.
• Migration notes or compatibility considerations (if applicable).