Improve loading speed of desktop app (#4865)

# Description of Changes
Improve loading speed of desktop app by loading a default config until
the backend has spawned.

frontend/src/desktop/components/AppProviders.tsx

@@ -1,5 +1,7 @@
 import { ReactNode } from "react";
 import { AppProviders as ProprietaryAppProviders } from "@proprietary/components/AppProviders";
+import { DesktopConfigSync } from '@app/components/DesktopConfigSync';
+import { DESKTOP_DEFAULT_APP_CONFIG } from '@app/config/defaultAppConfig';
 
 /**
  * Desktop application providers
@@ -13,7 +15,13 @@ export function AppProviders({ children }: { children: ReactNode }) {
         maxRetries: 5,
         initialDelay: 1000, // 1 second, with exponential backoff
       }}
+      appConfigProviderProps={{
+        initialConfig: DESKTOP_DEFAULT_APP_CONFIG,
+        bootstrapMode: 'non-blocking',
+        autoFetch: false,
+      }}
     >
+      <DesktopConfigSync />
       {children}
     </ProprietaryAppProviders>
   );

frontend/src/desktop/components/DesktopConfigSync.tsx

@@ -0,0 +1,23 @@
+import { useEffect, useRef } from 'react';
+import { useBackendHealth } from '@app/hooks/useBackendHealth';
+import { useAppConfig } from '@app/contexts/AppConfigContext';
+
+/**
+ * Desktop-only bridge that refetches the app config once the bundled backend
+ * becomes healthy (and whenever it restarts). Keeps the UI responsive by using
+ * default config until the real config is available.
+ */
+export function DesktopConfigSync() {
+  const { status } = useBackendHealth();
+  const { refetch } = useAppConfig();
+  const previousStatus = useRef(status);
+
+  useEffect(() => {
+    if (status === 'healthy' && previousStatus.current !== 'healthy') {
+      refetch();
+    }
+    previousStatus.current = status;
+  }, [status, refetch]);
+
+  return null;
+}