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

packages/ui/src/base/page/page.svelte

@@ -13,7 +13,10 @@
 <div
   bind:this={ref}
   data-slot="page"
-  class={cn('ui:flex ui:flex-col ui:gap-4 ui:min-h-[calc(100vh-48px)] ui:w-full', className)}
+  class={cn(
+    'ui:flex ui:flex-col ui:gap-4 ui:min-h-[calc(100vh-48px)] ui:w-full ui:overflow-x-hidden ui:md:overflow-x-auto',
+    className
+  )}
   {...restProps}
 >
   {@render children?.()}