test(app): align startup splash and host-page tests with desktop settings IPC

- Add testID="startup-splash" to the simplified splash screen so e2e helpers
  can detect desktop daemon bootstrap without depending on removed copy.
- Update startup-dsl helper to assert the testID instead of the deprecated
  "Starting local server..." text.
- Replace the obsolete localStorage write for manageBuiltInDaemon in the
  local-daemon sidebar test with a get_desktop_settings IPC mock so the
  desktop bridge surfaces the seeded host without triggering bootstrap.

packages/app/e2e/helpers/startup-dsl.ts

@@ -164,7 +164,7 @@ class StartupAssertions {
   }
 
   async expectsDesktopDaemonStartup(): Promise<this> {
-    await expect(this.page.getByText("Starting local server...", { exact: true })).toBeVisible({
+    await expect(this.page.getByTestId("startup-splash")).toBeVisible({
       timeout: 15_000,
     });
     return this;