refactor(desktop): drop dead boot overlay

Onboarding overlay subsumes the boot card now that it mounts from frame 1 and renders boot progress inline. The standalone DesktopBootOverlay is unreachable in every flow (yields whenever onboarding has not confirmed configured, dismisses once it has).

apps/desktop/src/app/desktop-controller.tsx

@@ -3,7 +3,6 @@ import { useQueryClient } from '@tanstack/react-query'
 import { lazy, Suspense, useCallback, useEffect, useRef } from 'react'
 import { Navigate, Route, Routes, useLocation, useNavigate, useParams } from 'react-router-dom'
 
-import { DesktopBootOverlay } from '@/components/desktop-boot-overlay'
 import { DesktopOnboardingOverlay } from '@/components/desktop-onboarding-overlay'
 import { Pane, PaneMain } from '@/components/pane-shell'
 import { useSkinCommand } from '@/themes/use-skin-command'
@@ -397,7 +396,6 @@ export function DesktopController() {
 
   const overlays = (
     <>
-      <DesktopBootOverlay />
       <DesktopOnboardingOverlay
         enabled={gatewayState === 'open'}
         onCompleted={() => {