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/package.json

@@ -56,6 +56,7 @@
     "d3-sankey": "^0.12.3",
     "dayjs": "^1.11.10",
     "encoding": "^0.1.13",
+    "hls.js": "^1.6.16",
     "hotkeys-js": "^3.11.2",
     "html-to-image": "^1.11.11",
     "is-valid-domain": "^0.1.6",
@@ -65,6 +66,7 @@
     "ky": "^1.10.0",
     "lodash": "^4.17.21",
     "marked": "^7.0.5",
+    "mediabunny": "^1.45.2",
     "openai-edge": "^1.2.2",
     "papaparse": "^5.4.1",
     "pluralize": "^8.0.0",