Update task instructions from old format to match English source:
- Old: "Add <kbd>padding: 1rem</kbd> to <kbd>.box</kbd>"
- New: "Set <kbd>padding</kbd> to <kbd>1rem</kbd>"
Removes redundant class name references since codePrefix shows the selector.
Affected languages: ar, es, pl, uk
- Create lesson directories and copy English lessons as templates
- Add full UI translations for pl, es, ar, uk languages
- Update lessons.js with module stores for all new languages
- Implement language cycling (en → de → pl → es → ar → uk → en)
- Fix playground mode detection (lesson.mode takes precedence)
