feat(FN-1076): integrate desktop IPC bridge and lifecycle modules

- Extract main-process IPC registration into src/ipc.ts for window controls, system info, tray status, updater checks, and native dialogs
- Refactor main.ts startup into initializeApp/run and wire menu, tray, deep-link, updater, and window-state restore/quit cleanup
- Rework preload bridge to expose typed window.fusionAPI subscriptions and replace preload.d.ts with shared src/types.d.ts global declarations
- Add comprehensive tests for IPC handlers, preload contracts, and main-process integration behavior
- Document IPC channels, preload API, and lifecycle sequencing in packages/desktop/README.md

packages/desktop/src/index.ts

@@ -1,15 +1,9 @@
-export {
-  createMainWindow,
-  setupTray,
-  updateTrayStatus,
-  registerIpcHandlers,
-  DASHBOARD_URL,
-  run,
-} from "./main.js";
+export { DASHBOARD_URL, createMainWindow, initializeApp, run } from "./main.js";
+export { registerIpcHandlers } from "./ipc.js";
 
-export { createTrayIcon, buildTrayContextMenu, getTrayTooltip } from "./tray.js";
-export { buildMenuTemplate, buildAppMenu } from "./menu.js";
+export * from "./tray.js";
+export * from "./menu.js";
+export * from "./native.js";
+export * from "./deep-link.js";
 
-export type { EngineStatus, TrayMenuOptions } from "./tray.js";
-export type { AppMenuOptions } from "./menu.js";
-export type { FusionDesktopAPI } from "./preload.js";
+export type { FusionAPI, SystemInfo, UpdateCheckResult } from "./types";