Map placeholders to the project's actual Crowdin language ids and drop the bogus bare keys (es, pt, zh) that aren't real Crowdin codes and broke crowdin-cli config validation. Add Arabic (ar) mapped to app_ar.arb so future syncs use underscore filenames instead of hyphenated ones (e.g. app_ar-SA.arb) that break Flutter gen-l10n.
- Change crowdin.yml to use %locale_with_underscore% for proper zh_CN/zh_TW handling
- Add sectionLanguage, appearanceLanguage, appearanceLanguageSubtitle to app_en.arb
- Add app_zh_CN.arb for Simplified Chinese (Crowdin target)
- Update .gitignore to exclude log files and tool/ folder
- Regenerate localization dart files