Add course management improvements: tree view, module descriptions, lesson toggles

- SortableModules: add description textarea in edit form, show description in row
- CourseDetailPage: fetch lessons per module, add CourseTree overview section
- ModulePage: fetch sibling modules, pass as otherModules to SortableLessons

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

src/app/admin/courses/[courseId]/modules/[moduleId]/page.tsx

@@ -10,13 +10,20 @@ interface Props {
 export default async function ModulePage({ params }: Props) {
   const { courseId, moduleId } = await params;
 
-  const module = await prisma.module.findUnique({
-    where: { id: moduleId },
-    include: {
-      course: { select: { title: true } },
-      lessons: { orderBy: { order: "asc" } },
-    },
-  });
+  const [module, allModules] = await Promise.all([
+    prisma.module.findUnique({
+      where: { id: moduleId },
+      include: {
+        course: { select: { title: true } },
+        lessons: { orderBy: { order: "asc" } },
+      },
+    }),
+    prisma.module.findMany({
+      where: { courseId, NOT: { id: moduleId } },
+      select: { id: true, title: true },
+      orderBy: { order: "asc" },
+    }),
+  ]);
 
   if (!module || module.courseId !== courseId) notFound();
 
@@ -41,7 +48,12 @@ export default async function ModulePage({ params }: Props) {
         <p className="text-xs font-bold uppercase tracking-widest mb-5" style={{ color: "var(--muted-foreground)" }}>
           Уроки модуля
         </p>
-        <SortableLessons courseId={courseId} moduleId={moduleId} lessons={module.lessons} />
+        <SortableLessons
+          courseId={courseId}
+          moduleId={moduleId}
+          lessons={module.lessons}
+          otherModules={allModules}
+        />
       </section>
     </div>
   );

src/app/admin/courses/[courseId]/page.tsx

@@ -4,6 +4,7 @@ import Link from "next/link";
 import { CourseEditForm } from "@/components/admin/course-edit-form";
 import { SortableModules } from "@/components/admin/sortable-modules";
 import { EnrollmentManager } from "@/components/admin/enrollment-manager";
+import { CourseTree } from "@/components/admin/course-tree";
 
 interface Props {
   params: Promise<{ courseId: string }>;
@@ -18,7 +19,13 @@ export default async function CourseDetailPage({ params }: Props) {
       include: {
         modules: {
           orderBy: { order: "asc" },
-          include: { _count: { select: { lessons: true } } },
+          include: {
+            _count: { select: { lessons: true } },
+            lessons: {
+              orderBy: { order: "asc" },
+              select: { id: true, title: true, published: true, kinescopeId: true },
+            },
+          },
         },
         enrollments: {
           select: { userId: true, expiresAt: true },
@@ -73,6 +80,16 @@ export default async function CourseDetailPage({ params }: Props) {
         <SortableModules courseId={courseId} modules={course.modules} />
       </section>
 
+      {/* Course tree overview */}
+      {course.modules.length > 0 && (
+        <section className="card-aubade p-6 mb-6">
+          <p className="text-xs font-bold uppercase tracking-widest mb-5" style={{ color: "var(--muted-foreground)" }}>
+            Структура курса
+          </p>
+          <CourseTree courseId={courseId} modules={course.modules} />
+        </section>
+      )}
+
       {/* Access management */}
       <section className="card-aubade p-6">
         <p className="text-xs font-bold uppercase tracking-widest mb-5" style={{ color: "var(--muted-foreground)" }}>