fix: resolve runtime issues with game loop, tabs, and error handling

- Fix game loop store mismatch (page.tsx was using old store, gameHooks using new store)
- Fix StatsTab.tsx calling getStudySpeedMultiplier with wrong arguments
- Add ErrorBoundary to page.tsx for better error handling
- Fix import syntax issues in page.tsx
- Ensure build succeeds with fixes

src/components/ErrorBoundary.tsx

@@ -0,0 +1,38 @@
+'use client';
+
+import { Component, ReactNode } from 'react';
+
+interface ErrorBoundaryProps {
+  children: ReactNode;
+  fallback?: ReactNode;
+}
+
+interface ErrorBoundaryState {
+  hasError: boolean;
+  error?: Error;
+}
+
+export class ErrorBoundary extends Component<ErrorBoundaryProps, ErrorBoundaryState> {
+  constructor(props: ErrorBoundaryProps) {
+    super(props);
+    this.state = { hasError: false };
+  }
+
+  static getDerivedStateFromError(error: Error): ErrorBoundaryState {
+    return { hasError: true, error };
+  }
+
+  render() {
+    if (this.state.hasError) {
+      return this.props.fallback || (
+        <div className="p-4 bg-red-900/20 border border-red-600/50 rounded">
+          <h3 className="text-red-400 font-bold mb-2">Something went wrong:</h3>
+          <pre className="text-xs text-red-300">{this.state.error?.message}</pre>
+          <pre className="text-xs text-gray-500 mt-2">{this.state.error?.stack}</pre>
+        </div>
+      );
+    }
+
+    return this.props.children;
+  }
+}