android(i18n): Add complete Chinese translation (#240)

This pull request is purely a localization effort and **does not add any new features or UI elements** to the Android application. Its sole purpose is to enable a complete Chinese (zh-CN) display in a Chinese Android environment.

Changes:
- All translatable strings from  now have corresponding translated entries in .
- This significantly improves the user experience for Chinese-speaking users.

Author: Gong-Mi