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" />

apps/web/src/app/(dashboard)/dashboard/learning/page.tsx

@@ -2,7 +2,8 @@
 
 import { useEffect, useState } from 'react';
 import Link from 'next/link';
-import { GraduationCap, BookOpen, Loader2, Trophy } from 'lucide-react';
+import { GraduationCap, BookOpen, Loader2, Trophy, Download } from 'lucide-react';
+import { Button } from '@/components/ui/button';
 import { Card, CardContent } from '@/components/ui/card';
 import { Progress } from '@/components/ui/progress';
 import { api } from '@/lib/api';
@@ -28,6 +29,13 @@ export default function LearningPage() {
   const [enrollments, setEnrollments] = useState<EnrollmentData[]>([]);
   const [loading, setLoading] = useState(true);
 
+  const handleDownloadCertificate = async (courseId: string) => {
+    try {
+      const { certificateUrl } = await api.getCertificate(courseId);
+      window.open(certificateUrl, '_blank');
+    } catch { /* silent */ }
+  };
+
   useEffect(() => {
     if (authLoading || !user) { setLoading(false); return; }
     (async () => {
@@ -97,6 +105,17 @@ export default function LearningPage() {
                       </div>
                       <Progress value={enrollment.progress} className="h-1.5" />
                     </div>
+                    {enrollment.completedAt && (
+                      <Button
+                        size="sm"
+                        variant="outline"
+                        className="w-full mt-3"
+                        onClick={(e) => { e.preventDefault(); handleDownloadCertificate(enrollment.course.id); }}
+                      >
+                        <Download className="mr-2 h-3.5 w-3.5" />
+                        Скачать сертификат
+                      </Button>
+                    )}
                   </CardContent>
                 </Card>
               </Link>