feat: detect new web builds + hard-refresh escape hatch (0.1.17/batch78)

Root cause of "the fix works on mobile but not on desktop/web": nothing was wrong with
the code — the desktop app now CLOSES TO TRAY, so it can run for weeks on the page it
loaded on day one and never re-fetch after a deploy. There was also no way to force it
off a stale page (no menu bar → no reload accelerator).

- Server: GET /api/build returns home.html's __BUILD marker.
- Client: polls it (boot, on focus/visibility, every 10 min); when the server's build
  differs from the running one, shows a branded "A new version is available — Refresh"
  banner. Settings gains an always-available "Refresh app" with the current build shown.
- hardReloadApp(): in the browser it unregisters service workers + clears CacheStorage
  then reloads cache-busted; in the shell it calls the native hard reload.
- Desktop: hard-reload IPC (clears the session HTTP cache + reloadIgnoringCache), wired to
  Ctrl+R (reload), Ctrl+Shift+R / F5 (hard reload), and a "Refresh app (get latest)" tray
  item. Previously there was literally no way to clear the cache from the app.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/routes.js

@@ -917,6 +917,17 @@ route('GET', '/api/meetings/config', (req, res) => {
   json(res, 200, { sfu: LIVEKIT_ENABLED, url: LIVEKIT_ENABLED ? LIVEKIT_URL : '' });
 });
 
+// The web build currently on the server (home.html's __BUILD marker). Long-running clients poll this and
+// offer a Refresh when it changes. This matters because the desktop app now CLOSES TO TRAY — it can run
+// for weeks without ever reloading the page, so it would silently keep serving stale code after a deploy.
+let APP_BUILD = '';
+try {
+  const h = fs.readFileSync(path.join(require('./config').PUBLIC_DIR, 'home.html'), 'utf8');
+  const m = /__BUILD='([^']+)'/.exec(h);
+  if (m) APP_BUILD = m[1];
+} catch (_) {}
+route('GET', '/api/build', (req, res) => json(res, 200, { build: APP_BUILD }));
+
 // Mint a LiveKit join token for the signed-in user + a specific room (the 6-digit meeting code).
 // The room-membership/host authorization already happens over the meeting WebSocket; this only
 // hands the client a media-plane credential scoped to that room and its own identity.