perf(router): lazy-load Lobby/Explore/Inbox routes; fix spoiler aria-pressed initial state

Lobby, Explore/FeaturedRooms/PublicRooms, Inbox/Notifications/Invites are
now lazy-loaded via React.lazy so they only enter the bundle when navigated
to. Main bundle: 2547 kB → 2472 kB (gzip 637 → 618 kB).

Spoiler aria-pressed was initialised to false (revealed); changed to true
so the spoiler starts hidden, matching CSS logic (aria-pressed=true →
color:transparent).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/plugins/react-custom-html-parser.tsx

@@ -466,7 +466,7 @@ export const getReactCustomHtmlParser = (
               onClick={params.handleSpoilerClick}
               className={css.Spoiler()}
               aria-label="Spoiler — click to reveal"
-              aria-pressed={false}
+              aria-pressed={true}
               style={{ cursor: 'pointer' }}
             >
               {domToReact(children, opts)}