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/routes/+layout.svelte

@@ -23,11 +23,6 @@
   onMount(() => {
     console.log('Layout', data);
 
-    const loadingIndicator = document.getElementById('app-loading-indicator');
-    if (loadingIndicator) {
-      loadingIndicator.style.display = 'none';
-    }
-
     const sessionUser = data?.locals?.user;
     setupCloudAnalytics(
       sessionUser ? { id: sessionUser.id, email: sessionUser.email, name: sessionUser.name } : undefined