fix: useState hook error in catalog + add certificate download in learning page

Co-authored-by: Cursor <cursoragent@cursor.com>

apps/web/src/app/(dashboard)/dashboard/catalog/[id]/page.tsx

@@ -34,6 +34,7 @@ export default function PublicCoursePage() {
   const [loading, setLoading] = useState(true);
   const [enrolling, setEnrolling] = useState(false);
   const [enrolled, setEnrolled] = useState(false);
+  const [expandedChapters, setExpandedChapters] = useState<string[]>([]);
 
   useEffect(() => {
     if (!id) return;
@@ -221,12 +222,19 @@ export default function PublicCoursePage() {
           <h2 className="text-xl font-semibold mb-4">Содержание курса</h2>
           <div className="space-y-2">
             {course.chapters.map((chapter: any) => {
-              const [expanded, setExpanded] = useState(false);
+              const expanded = expandedChapters.includes(chapter.id);
+              const toggleExpanded = () => {
+                setExpandedChapters(prev =>
+                  prev.includes(chapter.id)
+                    ? prev.filter(id => id !== chapter.id)
+                    : [...prev, chapter.id]
+                );
+              };
               return (
                 <div key={chapter.id} className="border rounded-lg overflow-hidden">
                   <button
                     className="flex items-center justify-between w-full p-4 hover:bg-muted/50 transition-colors"
-                    onClick={() => setExpanded(!expanded)}
+                    onClick={toggleExpanded}
                   >
                     <div className="flex items-center gap-3">
                       <BookOpen className="h-4 w-4 text-primary" />