Add lesson complete button with homework-aware logic

- Show "Отметить как пройденный" button only on lessons without homework
- Show static "Пройдено" badge on homework lessons completed via approval
- Auto-create LessonProgress when curator/admin approves homework submission
- Revalidate student lesson, course, and dashboard pages on approval

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

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

@@ -179,9 +179,12 @@ export default async function LessonPage({ params }: Props) {
           <div />
         )}
 
-        {!isAdmin && (
+        {!isAdmin && !lesson.homework && (
           <LessonCompleteButton lessonId={lessonId} slug={slug} isCompleted={isCompleted} />
         )}
+        {!isAdmin && lesson.homework && isCompleted && (
+          <LessonCompleteButton lessonId={lessonId} slug={slug} isCompleted={true} readOnly={true} />
+        )}
 
         {nextLesson ? (
           <Link