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/custom/org-landing-page/bold/vars.ts

@@ -0,0 +1,10 @@
+import { baseTokenVars, type LandingThemeVars } from '../theme-vars-base';
+
+export const vars: LandingThemeVars = {
+  ...baseTokenVars,
+  '--landing-heading-weight': '900',
+  '--landing-heading-tracking': '-0.02em',
+  '--landing-radius-card': '24px',
+  '--landing-shadow-card': '0 8px 24px -20px color-mix(in oklab, var(--landing-fg), transparent 80%)',
+  '--landing-divider': '1px solid var(--landing-border)'
+};