Synchronizes 72 lesson files across 5 languages (de, pl, es, ar, uk) to match
the English source. This ensures code, solutions, and validations are identical
while only title, description, task, and message fields are translated.
Changes include:
- Box model lessons (01-box-model.json)
- Units and variables (05-units-variables.json)
- Transitions and animations (06-transitions-animations.json)
- Responsive design (08-responsive.json)
- HTML elements (20-html-elements.json)
- HTML forms basic and validation (21, 22)
- HTML details/summary, progress/meter (23, 24)
- HTML datalist, dialog, fieldset (25, 27, 28)
- HTML tables and SVG (30, 32)
- HTML marquee (31)
- Welcome module (00-welcome.json)
Fixes validation inconsistencies and removes extra content that exceeded
English source. German translations were largely correct; Polish, Spanish,
Arabic, and Ukrainian required full translations.
- Fixed validation in welcome lesson (Hello World instead of Hello)
- Replaced 'quoted text' with <code>quoted text</code> in all task descriptions
- Added syntax examples to Transitions and Keyframes lessons
- Updated all language versions (en, de, pl, es, ar, 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)
