fase(25): polish and quality improvements

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/layout/ErrorBoundary.tsx

@@ -0,0 +1,54 @@
+import { Component, type ReactNode } from 'react'
+import { Button } from '@/components/ui/button'
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
+
+interface Props {
+  children: ReactNode
+  fallback?: ReactNode
+}
+
+interface State {
+  hasError: boolean
+  error: Error | null
+}
+
+export class ErrorBoundary extends Component<Props, State> {
+  constructor(props: Props) {
+    super(props)
+    this.state = { hasError: false, error: null }
+  }
+
+  static getDerivedStateFromError(error: Error): State {
+    return { hasError: true, error }
+  }
+
+  handleReset = () => {
+    this.setState({ hasError: false, error: null })
+  }
+
+  render() {
+    if (this.state.hasError) {
+      if (this.props.fallback) return this.props.fallback
+
+      return (
+        <div className="flex items-center justify-center min-h-[400px] p-6">
+          <Card className="w-full max-w-md">
+            <CardHeader>
+              <CardTitle className="text-destructive">Something went wrong</CardTitle>
+            </CardHeader>
+            <CardContent className="space-y-4">
+              <p className="text-sm text-muted-foreground">
+                {this.state.error?.message ?? 'An unexpected error occurred.'}
+              </p>
+              <Button onClick={this.handleReset} variant="outline">
+                Try again
+              </Button>
+            </CardContent>
+          </Card>
+        </div>
+      )
+    }
+
+    return this.props.children
+  }
+}