feat: show mark as complete only for students

apps/dashboard/src/routes/courses/[id]/lessons/[...lessonParams]/+page.svelte

@@ -298,6 +298,7 @@
       className="overflow-x-hidden"
     >
       <Materials lessonId={data.lessonId} {mode} {prevMode} {toggleMode} bind:isSaving />
+      {#if isStudent}
         <div class="w-full hidden lg:flex flex-row-reverse mt-10">
           <PrimaryButton
             onClick={() => markLessonComplete(data.lessonId)}
@@ -314,6 +315,7 @@
             Mark as {isLessonComplete ? 'Incomplete' : 'Complete'}
           </PrimaryButton>
         </div>
+      {/if}
     </PageBody>
   {/if}