fix(app): add ErrorBoundary to show actual crash errors instead of white screen

src/App.tsx

@@ -3,7 +3,8 @@
  * Handles routing and global providers
  */
 import { Routes, Route, useNavigate, useLocation } from 'react-router-dom';
-import { useEffect } from 'react';
+import { Component, useEffect } from 'react';
+import type { ErrorInfo, ReactNode } from 'react';
 import { Toaster } from 'sonner';
 import { MainLayout } from './components/layout/MainLayout';
 import { Dashboard } from './pages/Dashboard';
@@ -16,6 +17,70 @@ import { Setup } from './pages/Setup';
 import { useSettingsStore } from './stores/settings';
 import { useGatewayStore } from './stores/gateway';
 
+/**
+ * Error Boundary to catch and display React rendering errors
+ */
+class ErrorBoundary extends Component<
+  { children: ReactNode },
+  { hasError: boolean; error: Error | null }
+> {
+  constructor(props: { children: ReactNode }) {
+    super(props);
+    this.state = { hasError: false, error: null };
+  }
+
+  static getDerivedStateFromError(error: Error) {
+    return { hasError: true, error };
+  }
+
+  componentDidCatch(error: Error, info: ErrorInfo) {
+    console.error('React Error Boundary caught error:', error, info);
+  }
+
+  render() {
+    if (this.state.hasError) {
+      return (
+        <div style={{ 
+          padding: '40px', 
+          color: '#f87171', 
+          background: '#0f172a', 
+          minHeight: '100vh',
+          fontFamily: 'monospace'
+        }}>
+          <h1 style={{ fontSize: '24px', marginBottom: '16px' }}>Something went wrong</h1>
+          <pre style={{ 
+            whiteSpace: 'pre-wrap', 
+            wordBreak: 'break-all',
+            background: '#1e293b',
+            padding: '16px',
+            borderRadius: '8px',
+            fontSize: '14px'
+          }}>
+            {this.state.error?.message}
+            {'\n\n'}
+            {this.state.error?.stack}
+          </pre>
+          <button
+            onClick={() => { this.setState({ hasError: false, error: null }); window.location.reload(); }}
+            style={{
+              marginTop: '16px',
+              padding: '8px 16px',
+              background: '#3b82f6',
+              color: 'white',
+              border: 'none',
+              borderRadius: '6px',
+              cursor: 'pointer'
+            }}
+          >
+            Reload
+          </button>
+        </div>
+      );
+    }
+    return this.props.children;
+  }
+}
+
 function App() {
   const navigate = useNavigate();
   const location = useLocation();
@@ -69,7 +134,7 @@ function App() {
   }, [theme]);
   
   return (
-    <>
+    <ErrorBoundary>
       <Routes>
         {/* Setup wizard (shown on first launch) */}
         <Route path="/setup/*" element={<Setup />} />
@@ -91,7 +156,7 @@ function App() {
         richColors
         closeButton
       />
-    </>
+    </ErrorBoundary>
   );
 }