feat(desktop): split daemon and release settings to main process

Move daemon management and release channel settings out of the renderer's
AsyncStorage and into a desktop-owned settings store persisted by the main
process. Adds a "Keep daemon running after quit" option, a daemon lifecycle
section in settings, and a one-time migration of legacy renderer-owned
desktop settings.

packages/desktop/src/settings/desktop-settings-electron.ts

@@ -0,0 +1,12 @@
+import { app } from "electron";
+
+import { createDesktopSettingsStore, type DesktopSettingsStore } from "./desktop-settings.js";
+
+let desktopSettingsStore: DesktopSettingsStore | null = null;
+
+export function getDesktopSettingsStore(): DesktopSettingsStore {
+  desktopSettingsStore ??= createDesktopSettingsStore({
+    userDataPath: app.getPath("userData"),
+  });
+  return desktopSettingsStore;
+}