Fix Prisma 7 JSON proxy serialization in RSC props

Prisma 7 wraps Json fields in proxy objects that RSC cannot serialize.
Fix: select specific columns (exclude content) in module page,
and JSON.parse/stringify lesson content before passing to client.

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

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

@@ -15,7 +15,10 @@ export default async function ModulePage({ params }: Props) {
       where: { id: moduleId },
       include: {
         course: { select: { title: true } },
-        lessons: { orderBy: { order: "asc" } },
+        lessons: {
+          orderBy: { order: "asc" },
+          select: { id: true, title: true, order: true, published: true, kinescopeId: true },
+        },
       },
     }),
     prisma.module.findMany({