Add quiz feature: student UI, admin editor, lesson page integration

- QuizSection component: shows questions as text inputs, read-only after submission
- QuizEditor component: admin CRUD for quiz questions with type selector
- saveQuiz/deleteQuiz server actions for admin
- submitQuizAttempt server action: idempotent, auto-marks lesson complete
- Student lesson page: renders QuizSection, updates complete button logic
- Admin lesson page: renders QuizEditor below homework section

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/(student)/courses/[slug]/lessons/[lessonId]/page.tsx

@@ -7,6 +7,7 @@ import { KinescopePlayer } from "@/components/player/kinescope-player";
 import { LessonContent } from "@/components/student/lesson-content";
 import { LessonCompleteButton } from "@/components/student/lesson-complete-button";
 import { HomeworkSection } from "@/components/student/homework-section";
+import { QuizSection } from "@/components/student/quiz-section";
 import { LessonComments } from "@/components/student/lesson-comments";
 import { FileFormatBadge } from "@/components/shared/file-format-badge";
 
@@ -26,6 +27,9 @@ export default async function LessonPage({ params }: Props) {
       include: {
         files: { orderBy: { createdAt: "asc" } },
         homework: true,
+        quiz: {
+          include: { questions: { orderBy: { order: "asc" } } },
+        },
         module: {
           include: {
             course: {
@@ -71,6 +75,12 @@ export default async function LessonPage({ params }: Props) {
       })
     : null;
 
+  const quizAttempt = lesson?.quiz && session && !isAdmin
+    ? await prisma.quizAttempt.findFirst({
+        where: { quizId: lesson.quiz.id, userId: session.user.id },
+      })
+    : null;
+
   if (!lesson || lesson.module.course.slug !== slug) notFound();
 
   const isCompleted = !!progress;
@@ -163,6 +173,21 @@ export default async function LessonPage({ params }: Props) {
         </div>
       )}
 
+      {/* Quiz */}
+      {lesson.quiz && !isAdmin && (
+        <div className="mb-8">
+          <p className="text-xs font-bold uppercase tracking-widest mb-3" style={{ color: "var(--muted-foreground)" }}>
+            Тест
+          </p>
+          <QuizSection
+            quiz={lesson.quiz}
+            attempt={quizAttempt ? { answers: quizAttempt.answers as Record<string, string> } : null}
+            slug={slug}
+            lessonId={lessonId}
+          />
+        </div>
+      )}
+
       {/* Complete button + Prev/Next navigation */}
       <div
         className="flex items-center justify-between pt-6 mt-6"
@@ -179,10 +204,10 @@ export default async function LessonPage({ params }: Props) {
           <div />
         )}
 
-        {!isAdmin && !lesson.homework && (
+        {!isAdmin && !lesson.homework && !lesson.quiz && (
           <LessonCompleteButton lessonId={lessonId} slug={slug} isCompleted={isCompleted} />
         )}
-        {!isAdmin && lesson.homework && isCompleted && (
+        {!isAdmin && (lesson.homework || lesson.quiz) && isCompleted && (
           <LessonCompleteButton lessonId={lessonId} slug={slug} isCompleted={true} readOnly={true} />
         )}