Document localization review lessons - #12

Summary

• document why the previous localization pass had quality issues
• define the required full-surface review scope for UI translations and localized SEO templates
• list the checks and manual scan rules required for future localized copy changes
• link the checklist from CONTRIBUTING.md

Verification

• npm run lint
• git diff --check

Root cause captured

• synthetic generator was easy to invoke by mistake
• review started from affected tools and did not begin with full localized JSON coverage
• existing gates caught key/rendering regressions but not language-quality defects
• checked-in localized SEO files under generated/ were still user-facing copy and must be reviewed as such