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/utils/src/validation/course/course.ts

@@ -315,6 +315,8 @@ export const ZCourseMetadata = z.object({
   instructor: ZCourseInstructor.optional(),
   certificate: ZCourseCertificate.optional(),
   reviews: z.array(ZCourseReview).optional(),
+  skills: z.array(z.string().min(1).max(80)).max(60).optional(),
+  tools: z.array(z.string().min(1).max(80)).max(60).optional(),
   lessonTabsOrder: ZCourseLessonTabsOrder.optional(),
   grading: z.boolean().optional(),
   lessonDownload: z.boolean().optional(),
@@ -336,6 +338,8 @@ export const ZCourseLandingPageMetadataUpdate = z.object({
   instructor: ZCourseInstructor.partial().optional(),
   certificate: ZCourseCertificate.partial().optional(),
   reviews: z.array(ZCourseReview).optional(),
+  skills: z.array(z.string().min(1).max(80)).max(60).optional(),
+  tools: z.array(z.string().min(1).max(80)).max(60).optional(),
   lessonTabsOrder: ZCourseLessonTabsOrder.optional(),
   grading: z.boolean().optional(),
   lessonDownload: z.boolean().optional(),