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/website/src/lib/components/hero.svelte

@@ -109,7 +109,7 @@
   <div class="relative z-30 mx-auto mt-14 w-full max-w-[1100px]">
     <div class="overflow-hidden rounded-2xl bg-white shadow-sm ring-1 ring-gray-200">
       <img
-        src="/hero-academy.jpeg"
+        src="https://assets.cdn.clsrio.com/www/home/hero-academy.jpeg"
         alt="Branded customer academy on a custom domain — catalog, programs, AI tutor"
         width="2560"
         height="1440"