Add Simplified Chinese localization

[YspritanHyzygy]

Summary

• Add a bundled zh-Hans Simplified Chinese translation without replacing the existing Traditional Chinese zh locale.
• Resolve common Simplified and Traditional Chinese device locale tags to the correct bundled language.
• Merge bundled language metadata and dictionaries with cached or remote data so a new bundled locale remains available when those sources are stale.
• Localize built-in prompt and resource display labels.
• Replace the invalid starter counter test with localization regression checks.

The unrelated Android, resource-link, and Dart cleanup changes from the original combined submission were extracted to #39.

Validation

• Parsed all bundled translation JSON files with jq.
• Verified the Simplified Chinese dictionary has exactly the same keys as the English dictionary.
• Verified the bundled language IDs are unique and include zh-Hans.
• Verified pubspec.yaml registers the Simplified Chinese asset.
• git diff --check upstream/main
• git merge-tree --write-tree codex/simplified-chinese-localization codex/maintenance-fixes (clean merge with Fix Android setup and clean up Dart code #39)

flutter analyze and flutter test were not rerun in the current environment because no Flutter SDK is installed. The original combined commit reported both checks passing; this split retains the same production changes and separates the regression tests by topic.

[Puzzak]

Holy heck, you really did dig into my bad code. Thanks, I will try my best to review it soon!

What a legend