v0.2.0

feat: full i18n coverage + sidebar language switcher

- All hardcoded strings moved to locales (en + zh-CN)
- Added scan.idle, scan.tidy, scan.files, scan.all, clean.errors,
  settings.language, settings.about, settings.version, settings.license,
  common.more_files keys
- Sidebar: language toggle (EN / 中文) always visible at bottom
- ScanPage, SettingsPage, CategoryList: use t() for all user-facing text
- SettingsPage: version bumped to 0.2.0

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>