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/jobs/src/index.ts

@@ -4,9 +4,10 @@ import './workers/media';
 import './workers/media-transcribe';
 import './workers/emails';
 import './workers/maintenance';
+import './workers/agent-course-generation';
 
 import { log } from './utils/logger';
 
 log.info('all-workers-running', {
-  workers: ['media', 'media-transcribe', 'emails', 'maintenance']
+  workers: ['media', 'media-transcribe', 'emails', 'maintenance', 'agent-course-generation']
 });