fix #289: add localized date format

[wellorbetter]

Use string resource for date format to adapt to different locales.

Type of change(s)

• Bug fix
• Feature / enhancement
• Infrastructure / tooling (CI, build, deps, tests)
• Documentation

What changed and why

• Moved the date format from hardcoded logic to a localized string resource (R.string.date_format_md).
  This allows the date display (e.g., "Wed, 25 Mar" / "3月25日 周三" / "3月25日(水)") to automatically adapt to different locales without code changes.
• Updated the main clock to use this localized format.
• Added Korean and Japanese string resources for the date format to support those locales properly.

Tests performed

• Verified on device with English (US), Chinese (Simplified), Korean, and Japanese system languages.
• Ensured format falls back to English when locale resource is missing.

Closes the following issue(s)

• Closes Localization of date should not be order-dependent #289

Checklist

• I read the contribution guidelines.
• I manually tested my changes on device/emulator (if applicable).
• I updated the "Unreleased" section in CHANGELOG.md (if applicable).
• I have self-reviewed my pull request (no typos, formatting errors, etc.).
• I understand every change in this pull request.