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

src/i18n.js

@@ -76,6 +76,10 @@ const translations = {
 		emmetNested: "<kbd>form>input+button</kbd> → nested structure",
 		emmetContent: "<kbd>p{Hello}</kbd> → p with text content",
 
+		// Contact
+		contactTitle: "Contact & Links",
+		contactText: "Code Crispies is developed by librete.ch",
+
 		// Reset dialog
 		resetDialogTitle: "Reset Progress",
 		resetDialogText: "Are you sure you want to reset all your progress? This cannot be undone.",
@@ -165,6 +169,10 @@ const translations = {
 		emmetNested: "<kbd>form>input+button</kbd> → verschachtelte Struktur",
 		emmetContent: "<kbd>p{Hallo}</kbd> → p mit Textinhalt",
 
+		// Contact
+		contactTitle: "Kontakt & Links",
+		contactText: "Code Crispies wird von librete.ch entwickelt",
+
 		// Reset dialog
 		resetDialogTitle: "Fortschritt zurücksetzen",
 		resetDialogText: "Bist du sicher, dass du deinen gesamten Fortschritt zurücksetzen möchtest? Dies kann nicht rückgängig gemacht werden.",