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/06-transitions-animations.json

@@ -1,7 +1,7 @@
 {
 	"$schema": "../schemas/code-crispies-module-schema.json",
 	"id": "transitions-animations",
-	"title": "Animations",
+	"title": "CSS Animations",
 	"description": "Bring interactivity to your UI by smoothly transitioning properties and creating keyframe-driven animations.",
 	"difficulty": "beginner",
 	"lessons": [