fix: clear current module/lesson when reloading modules for language switch

When setModules is called (e.g., during language switch), clear currentModule
and currentLesson to force fresh lookup from the new modules array. This
prevents stale module objects from the old language being used.

src/impl/LessonEngine.js

@@ -23,6 +23,9 @@ export class LessonEngine {
 	 */
 	setModules(modules) {
 		this.modules = modules;
+		// Clear current module/lesson to force reload with new language content
+		this.currentModule = null;
+		this.currentLesson = null;
 		this.loadUserCodeFromStorage();
 	}