feat: HLS streaming, transcripts, agent course generation & landing-page course previews (#663)

New features:
- HLS video encoding/streaming (hls routes, hls-encoder) and a media
  transcripts pipeline (transcripts route + media-transcript queries)
- AI assistant chat vs. run model: agent-course-generation worker/queue,
  run-monitor pane, chat-changes card, content ask-ai bar
- Per-theme course-page previews across org landing-page themes (bold,
  classic, corporate, editorial, etc.) with a shared course token/component set
- View-as-student mode and login-link / link-invite invite flows

Refactor:
- Extract packages/core consolidating config (env, storage, dashboard-url),
  services and utils previously duplicated under apps/api/src/config
- Remove legacy agent service modules (chat-tools, chat-context,
  context-window, document, fetch-url, lesson-content)
- Relax Cross-Origin-Resource-Policy to allow cross-origin media embedding
- Add format script to tenant-router so turbo run format covers it

apps/dashboard/src/lib/features/ai-assistant/index.ts

@@ -1,4 +1,5 @@
 export { default as AiCourseChat } from './ai-course-chat.svelte';
+export { default as ContentAskAiBar } from './content-ask-ai-bar.svelte';
 export { default as PlanView } from './plan-view.svelte';
 export { default as ProgressCard } from './progress-card.svelte';
 export {
@@ -8,6 +9,7 @@ export {
   openAiAssistant,
   closeAiAssistant,
   quoteInChat,
+  sendPromptToAssistant,
   setChatDraft,
   toggleAiAssistant
 } from './utils/store';