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/landing-page-footer.tokens.ts

@@ -195,7 +195,7 @@ export function getFooterTokens(variant: OrgLandingPageTheme): FooterRegionToken
       bottomRow:
         'ui:flex ui:flex-col ui:gap-3 ui:sm:flex-row ui:sm:items-center ui:sm:justify-between ui:mt-14 ui:pt-6 ui:border-t ui:border-[var(--landing-border)]/60 ui:text-sm ui:text-[var(--landing-fg-muted)]',
       brandName:
-        'ui:font-bold ui:text-[42px] ui:md:text-[48px] ui:tracking-tight ui:text-[var(--landing-fg)] ui:flex ui:items-center ui:gap-3 ui:no-underline ui:break-words',
+        'ui:font-bold ui:text-2xl ui:md:text-3xl ui:tracking-tight ui:text-[var(--landing-fg)] ui:flex ui:items-center ui:gap-3 ui:no-underline ui:break-words',
       brandTagline:
         'ui:text-base ui:text-[var(--landing-fg-muted)] ui:break-words ui:mt-4 ui:max-w-[280px] ui:leading-relaxed',
       columnHeading: