feat(electron): electron shell skeleton (#8127)

fix AF-1331
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missing
- per split view skeleton
- per route skeleton

packages/frontend/electron/renderer/app.tsx

@@ -115,7 +115,7 @@ export function App() {
             <DebugProvider>
               <GlobalLoading />
               <RouterProvider
-                fallbackElement={<AppFallback key="RouterFallback" />}
+                fallbackElement={<AppFallback />}
                 router={router}
                 future={future}
               />