Allow admin to preview unpublished lessons without enrollment

- Course layout skips enrollment and published checks for admin role
- Lesson page skips published filter for admin role
- Enables admin preview button to work for any lesson/course state

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

src/app/(student)/courses/[slug]/layout.tsx

@@ -15,8 +15,10 @@ export default async function CourseLayout({ children, params }: Props) {
   const session = await auth.api.getSession({ headers: await headers() });
   if (!session) redirect("/login");
 
+  const isAdmin = session.user.role === "admin";
+
   const course = await prisma.course.findUnique({
-    where: { slug, published: true },
+    where: { slug, ...(isAdmin ? {} : { published: true }) },
     include: {
       modules: {
         orderBy: { order: "asc" },
@@ -33,14 +35,16 @@ export default async function CourseLayout({ children, params }: Props) {
 
   if (!course) notFound();
 
-  const enrollment = await prisma.courseEnrollment.findUnique({
-    where: { userId_courseId: { userId: session.user.id, courseId: course.id } },
-  });
+  if (!isAdmin) {
+    const enrollment = await prisma.courseEnrollment.findUnique({
+      where: { userId_courseId: { userId: session.user.id, courseId: course.id } },
+    });
 
-  if (!enrollment) redirect("/dashboard");
+    if (!enrollment) redirect("/dashboard");
 
-  if (enrollment.expiresAt && enrollment.expiresAt < new Date()) {
-    redirect("/dashboard?expired=1");
+    if (enrollment.expiresAt && enrollment.expiresAt < new Date()) {
+      redirect("/dashboard?expired=1");
+    }
   }
 
   return (