fix(desktop): app icon + harden auto-updater loading

Generate a 1024x1024 macOS app icon from the dashboard logo so packaged
builds carry the Fusion brand instead of the default Electron icon, and
load electron-updater dynamically inside a try/catch so packaged builds
tolerate CJS/ESM interop quirks and missing transitive deps. Widen the
electron-builder files whitelist to include electron-updater's
transitive dep tree so they are actually bundled into the asar.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/desktop/src/__tests__/native.test.ts

@@ -96,6 +96,7 @@ vi.mock("electron", () => ({
 }));
 
 vi.mock("electron-updater", () => ({
+  default: { autoUpdater: mocks.autoUpdater },
   autoUpdater: mocks.autoUpdater,
 }));