feat: add contact section and smooth lesson transitions

- Add contact section to help dialog with librete.ch, GitHub, Gitea, LinkedIn links
- Add HTML/CSS prefixes to English module titles for consistency with German
- Add CSS transitions for smooth lesson switching
- Add transitioning class to prevent content flash during lesson changes

lessons/08-responsive.json

@@ -1,7 +1,7 @@
 {
 	"$schema": "../schemas/code-crispies-module-schema.json",
 	"id": "responsive-design",
-	"title": "Responsive",
+	"title": "CSS Responsive Design",
 	"description": "Make your layouts adapt to different screen sizes using media queries and fluid design techniques.",
 	"difficulty": "intermediate",
 	"lessons": [