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/app.html

@@ -10,61 +10,9 @@
     <link rel="icon" type="image/png" sizes="32x32" href="/logo-32.png" />
 
     %sveltekit.head%
-    <style id="app-loading-styles">
-      #app-loading-indicator {
-        position: fixed;
-        inset: 0;
-        display: flex;
-        flex-direction: column;
-        align-items: center;
-        justify-content: center;
-        background: #fff;
-        z-index: 99999;
-      }
-      #app-loading-indicator .spinner {
-        width: 3.5rem;
-        height: 3.5rem;
-        color: #1d4ed8;
-        animation: app-loading-spin 1s linear infinite;
-      }
-      @keyframes app-loading-spin {
-        to {
-          transform: rotate(360deg);
-        }
-      }
-      #app-loading-indicator p {
-        margin-top: 16px;
-        color: #6b7280;
-        font-family: system-ui, sans-serif;
-      }
-    </style>
   </head>
 
   <body data-sveltekit-preload-data="hover" class="">
-    <div id="app-loading-indicator">
-      <svg
-        class="spinner"
-        xmlns="http://www.w3.org/2000/svg"
-        viewBox="0 0 24 24"
-        fill="none"
-        stroke="currentColor"
-        stroke-width="2"
-        stroke-linecap="round"
-        stroke-linejoin="round"
-        role="status"
-        aria-label="Loading"
-      >
-        <path d="M12 2v4" />
-        <path d="m16.2 7.8 2.9-2.9" />
-        <path d="M18 12h4" />
-        <path d="m16.2 16.2 2.9 2.9" />
-        <path d="M12 18v4" />
-        <path d="m4.9 19.1 2.9-2.9" />
-        <path d="M2 12h4" />
-        <path d="m4.9 4.9 2.9 2.9" />
-      </svg>
-      <p>Loading...</p>
-    </div>
     <div style="display: contents" class="theme-container">%sveltekit.body%</div>
   </body>
 </html>