feat(dashboard): add Show transcript and Summarize lesson buttons in lesson view (#748)

* feat(dashboard): add lesson transcript and summarize actions in view mode

Add Show transcript and Summarize lesson outline buttons beneath lesson
videos in view mode. Show transcript opens the existing transcript side
panel when an uploaded video has a transcript. Summarize lesson appears
on every lesson and sends a contextual prompt to the AI assistant.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(dashboard): localize summarize lesson AI prompts

Move hardcoded summarize prompt strings into translation keys so the
prompt sent to the AI assistant follows the user's app language.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

apps/dashboard/src/lib/features/course/pages/lesson.svelte

@@ -46,7 +46,8 @@
     Document,
     AddVideoModal,
     AddDocumentModal,
-    LessonSettingsTab
+    LessonSettingsTab,
+    LessonSummarizeButton
   } from '$features/course/components/lesson';
 
   import type { TLocale } from '@cio/db/types';
@@ -179,6 +180,7 @@
   const viewModeComponents = $derived(getViewModeComponents(tabs));
 
   const isMaterialsEmpty = $derived(tabs.every((tab) => tab.badgeValue === 0));
+  const hasLessonVideos = $derived((lessonApi.lesson?.videos?.length ?? 0) > 0);
 
   let timeoutId: NodeJS.Timeout | undefined;
 
@@ -524,6 +526,12 @@
       {:else if lessonApi.lesson && !isMaterialsEmpty}
         {#key lessonId}
           <div class="mb-20 flex w-full flex-col gap-2" in:fade={{ delay: 500 }} out:fade>
+            {#if !hasLessonVideos}
+              <div class="mb-2 flex flex-wrap gap-2">
+                <LessonSummarizeButton {lessonId} />
+              </div>
+            {/if}
+
             {#each viewModeComponents as Component, index (index)}
               <Component {mode} {lessonId} {courseId} />
             {/each}