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/core/hooks/tools/shared/useToolOperation.ts

@@ -12,6 +12,7 @@ import { ResponseHandler } from '@app/utils/toolResponseProcessor';
 import { createChildStub, generateProcessedFileMetadata } from '@app/contexts/file/fileActions';
 import { ToolOperation } from '@app/types/file';
 import { ToolId } from '@app/types/toolId';
+import { ensureBackendReady } from '@app/services/backendReadinessGuard';
 
 // Re-export for backwards compatibility
 export type { ProcessingProgress, ResponseHandler };
@@ -187,6 +188,12 @@ export const useToolOperation = <TParams>(
       return;
     }
 
+    const backendReady = await ensureBackendReady();
+    if (!backendReady) {
+      actions.setError(t('backendHealth.offline', 'Embedded backend is offline. Please try again shortly.'));
+      return;
+    }
+
     // Reset state
     actions.setLoading(true);
     actions.setError(null);

frontend/src/core/hooks/useBackendHealth.ts

@@ -0,0 +1,12 @@
+import type { BackendHealthState } from '@app/types/backendHealth';
+
+export function useBackendHealth(): BackendHealthState {
+  return {
+    status: 'healthy',
+    message: null,
+    isChecking: false,
+    lastChecked: Date.now(),
+    error: null,
+    isHealthy: true,
+  };
+}