perf: load the Settings dialog on demand; entry chunk 351.8 → 277.1 kB gzip

Settings (every page, pickers, the denoise tester) was in the entry
chunk though it only renders when opened. Load it lazily behind a
focusable spinner (it opens inside a FocusTrap), and warm the chunk
when the app goes idle. SettingsPages and the status localStorage keys
move to tiny modules so callers don't pull the dialog back in.
sanitize-html (+postcss, htmlparser2) and chroma-js get their own vendor
chunks; with Settings gone the chunk graph had dropped them into the
entry chunk.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/app/features/settings/Settings.tsx

@@ -33,16 +33,9 @@ import { About } from './about';
 import { UseStateProvider } from '../../components/UseStateProvider';
 import { stopPropagation } from '../../utils/keyboard';
 import { LogoutDialog } from '../../components/LogoutDialog';
+import { SettingsPages } from './pages';
 
-export enum SettingsPages {
-  GeneralPage,
-  AccountPage,
-  NotificationPage,
-  DevicesPage,
-  EmojisStickersPage,
-  DeveloperToolsPage,
-  AboutPage,
-}
+export { SettingsPages };
 
 type SettingsMenuItem = {
   page: SettingsPages;