Add self-contained shareable HTML export for YouTube recaps

New 'Share page (HTML)' entry in the Export menu generates a single
standalone .html file: the recap record inlined as JSON plus a small
baked-in renderer that reproduces the embedded YouTube player and the
expandable timestamped summaries. The recipient opens it with no account
and no calls back to the server. On mobile it hands the file to the
native share sheet (navigator.share with files); on desktop or where
unsupported it downloads.

YouTube only by design — podcasts have no portable audio and are
rejected with a toast. The generator runs inside index.html's own
<script>, so closing tags are split and inlined JSON escapes '<' to
avoid premature script termination.

Ship as 0.2.160.

startos/versions/v0.2.160.ts

@@ -0,0 +1,13 @@
+import { VersionInfo } from '@start9labs/start-sdk'
+
+export const v_0_2_160 = VersionInfo.of({
+  version: '0.2.160:0',
+  releaseNotes: {
+    en_US:
+      'New: Share page (HTML) export for YouTube recaps. The Export menu now offers a self-contained .html file with the embedded video and expandable timestamped summaries baked in — send it to anyone and they can open it with no account. On mobile it opens the native share sheet; on desktop it downloads.',
+  },
+  migrations: {
+    up: async ({ effects }) => {},
+    down: async ({ effects }) => {},
+  },
+})