feat: wire web app infrastructure

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

web/src/app/App.tsx

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+import { AppProviders } from "@/app/providers";
+
+export function App() {
+  return <AppProviders />;
+}

web/src/app/AppErrorBoundary.tsx

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+import { Component, type ErrorInfo, type ReactNode } from "react";
+
+interface Props {
+  children: ReactNode;
+}
+
+interface State {
+  hasError: boolean;
+  message?: string;
+}
+
+/** Minimal error boundary that renders a dark fallback panel. */
+export class AppErrorBoundary extends Component<Props, State> {
+  state: State = { hasError: false };
+
+  static getDerivedStateFromError(error: Error): State {
+    return { hasError: true, message: error.message };
+  }
+
+  componentDidCatch(error: Error, info: ErrorInfo) {
+    console.error("Uncaught application error:", error, info);
+  }
+
+  render() {
+    if (this.state.hasError) {
+      return (
+        <div className="flex min-h-screen flex-col items-center justify-center gap-2 bg-neutral-950 p-8 text-neutral-100">
+          <h1 className="text-lg font-semibold">Something went wrong</h1>
+          {this.state.message && (
+            <p className="text-sm text-neutral-400">{this.state.message}</p>
+          )}
+          <button
+            type="button"
+            className="mt-2 rounded-md border border-neutral-700 px-3 py-1 text-sm text-neutral-300 hover:bg-neutral-800"
+            onClick={() => window.location.reload()}
+          >
+            Reload
+          </button>
+        </div>
+      );
+    }
+    return this.props.children;
+  }
+}

web/src/app/providers.tsx

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+import { useState } from "react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { RouterProvider } from "react-router";
+
+import { router } from "@/app/router";
+import { AppErrorBoundary } from "@/app/AppErrorBoundary";
+
+export function AppProviders() {
+  const [queryClient] = useState(
+    () =>
+      new QueryClient({
+        defaultOptions: {
+          queries: {
+            staleTime: 60_000,
+            retry: 1,
+            refetchOnWindowFocus: false,
+          },
+        },
+      }),
+  );
+
+  return (
+    <AppErrorBoundary>
+      <QueryClientProvider client={queryClient}>
+        <RouterProvider router={router} />
+      </QueryClientProvider>
+    </AppErrorBoundary>
+  );
+}

web/src/app/router.tsx

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+import { createBrowserRouter } from "react-router";
+
+import { WorkspacePage } from "@/pages/workspace/WorkspacePage";
+
+export const router = createBrowserRouter([
+  {
+    path: "/",
+    element: <WorkspacePage />,
+  },
+]);