- Shorten German module titles with consistent HTML/CSS prefixes
- Add .completion-badge styling for the lesson title completion badge
- Make sidebar lessons section fill available height on desktop
- Improve flexbox lesson descriptions with more context
Prevent HTML elements like <details>, <option>, <form> from being
rendered as actual elements in hint messages by properly escaping
them with < > and wrapping in <kbd> tags.
- Wrap HTML element names in <kbd> tags in all validation messages
- Apply consistent formatting to both English and German lessons
- Make hints clearer about which elements/attributes to use
- Fix mobile editor layout overflow issue