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/(auth)/signup/+page.svelte

@@ -7,7 +7,7 @@
   import { page } from '$app/state';
   import { capturePosthogEvent } from '$lib/utils/services/posthog';
   import { globalStore } from '$lib/utils/store/app';
-  import { currentOrg } from '$lib/utils/store/org';
+  import { currentOrg, isFreePlan } from '$lib/utils/store/org';
   import { authClient } from '$lib/utils/services/auth/client';
   import * as Field from '@cio/ui/base/field';
   import { Input } from '@cio/ui/base/input';
@@ -177,7 +177,9 @@
   <title>Join ClassroomIO</title>
 </svelte:head>
 
-<SenjaEmbed id="aa054658-1e15-4d00-8920-91f424326c4e" />
+{#if !$globalStore.isOrgSite || $isFreePlan}
+  <SenjaEmbed id="aa054658-1e15-4d00-8920-91f424326c4e" />
+{/if}
 
 {#if signupRestricted}
   <div