Don't block desktop app on backend starting up (#5041)

# Description of Changes
Start bundled backend instantly on startup of app and don't wait on it
being fully up to spawn app. This is techincally wasteful curently on
self-hosted mode where everything runs remotely, but in the future we'll
probably route simple operations to the local machine regardless of
connection, and it stops unnecessary waiting in the offline mode.

frontend/src/desktop/components/AppProviders.tsx

@@ -31,10 +31,10 @@ export function AppProviders({ children }: { children: ReactNode }) {
     }
   }, [setupComplete, isFirstLaunch, connectionMode]);
 
-  // Only start bundled backend if in SaaS mode (local backend) and setup is complete
-  // Self-hosted mode connects to remote server so doesn't need local backend
-  const shouldStartBackend = setupComplete && !isFirstLaunch && connectionMode === 'saas';
-  useBackendInitializer(shouldStartBackend);
+  // Initialize monitoring for bundled backend (already started in Rust)
+  // This sets up port detection and health checks
+  const shouldMonitorBackend = setupComplete && !isFirstLaunch && connectionMode === 'saas';
+  useBackendInitializer(shouldMonitorBackend);
 
   // Show setup wizard on first launch
   if (isFirstLaunch && !setupComplete) {
@@ -51,23 +51,7 @@ export function AppProviders({ children }: { children: ReactNode }) {
         }}
       >
         <SetupWizard
-          onComplete={async () => {
-            // Wait for backend to become healthy before reloading
-            // This prevents reloading mid-startup which would interrupt the backend
-            const maxWaitTime = 60000; // 60 seconds max
-            const checkInterval = 1000; // Check every second
-            const startTime = Date.now();
-
-            while (Date.now() - startTime < maxWaitTime) {
-              if (tauriBackendService.isBackendHealthy()) {
-                window.location.reload();
-                return;
-              }
-              await new Promise(resolve => setTimeout(resolve, checkInterval));
-            }
-
-            // If we timeout, reload anyway
-            console.warn('[AppProviders] Backend health check timeout, reloading anyway...');
+          onComplete={() => {
             window.location.reload();
           }}
         />

frontend/src/desktop/components/SetupWizard/index.tsx

@@ -61,7 +61,7 @@ export const SetupWizard: React.FC<SetupWizardProps> = ({ onComplete }) => {
       }
 
       await connectionModeService.switchToSaaS(serverConfig.url);
-      await tauriBackendService.startBackend();
+      tauriBackendService.startBackend().catch(console.error);
       onComplete();
     } catch (err) {
       console.error('SaaS login failed:', err);