fix(#943): wrap Statistics in ErrorBoundary with retry fallback

[Coredevjay]

Summary

Closes #943.

The Statistics component had no error isolation — any unhandled rendering exception propagated straight to the page root, causing a full blank-screen crash. This PR wires up the existing ErrorBoundary around Statistics in LandingPage and improves the fallback UI with a retry affordance.

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Changes

frontend/src/components/LandingPage.tsx

• The ErrorBoundary wrapper that already existed around <Statistics /> had a fallback <section> with no way for the user to recover.
• Added a Retry button (aria-label="Retry loading statistics") inside that fallback, using the pre-existing .retry-button CSS class from Statistics.css.
• Clicking the button calls window.location.reload(), giving users a clear escape route when the component crashes rather than staring at a static error message.

frontend/src/components/__tests__/Statistics.test.tsx

• Imported ErrorBoundary from ../ErrorBoundary.
• Added a new describe('Statistics wrapped in ErrorBoundary') block with three focused unit tests:
  1. Catches a rendering exception — mounts <ErrorBoundary><ThrowingStatistics /></ErrorBoundary> and asserts the fallback heading, alert role, and message are rendered.
  2. Retry button is present — asserts getByRole('button', { name: /retry loading statistics/i }) is in the fallback.
  3. Statistics content is absent — asserts none of the normal stat labels ("Total Markets", "Total Volume", "Active Users") appear when the boundary has caught an error.
• Added a ThrowingStatistics helper component that unconditionally throws to simulate a runtime rendering exception.
• console.error is suppressed per test to keep output clean; restored via afterEach.

frontend/src/components/__tests__/LandingPage.error-boundary.test.tsx

• Extended the existing 'should render error fallback when Statistics throws' test to also assert that the retry button is rendered, keeping the integration test in sync with the new fallback UI.

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Acceptance Criteria

Criterion	Status
Statistics wrapped in ErrorBoundary from src/components/ErrorBoundary.tsx	✅ Already in place via LandingPage.tsx; this PR adds the missing retry affordance
Fallback UI shows a placeholder stats card with a retry button	✅ Done
Test that throws inside Statistics and verifies ErrorBoundary catches it and renders the fallback	✅ Three tests added in Statistics.test.tsx

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Testing

No new dependencies. Tests are in Jest + React Testing Library (already set up in the project).

cd frontend
npm test -- --testPathPattern="Statistics|LandingPage.error-boundary"

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