Feature/server error page and boundries

[awwalmust]

Description

Resolves #349

Implements application-wide and localized React Error Boundaries alongside a custom _error.tsx page to prevent unhandled render exceptions from unmounting the tree to a blank white screen.

Key Changes

• Global & Local Error Boundaries (frontend/components/ErrorBoundary.tsx):
  • Implemented ErrorBoundary class component with getDerivedStateFromError and componentDidCatch.
  • Added route-change reset behavior via keying on router.asPath in _app.tsx.
• Server Error Page (frontend/pages/_error.tsx):
  • Added custom SSR error page handling server-side rendering exceptions.
• Widget Isolation:
  • Wrapped high-risk components (TransactionGraphVisualizer, charts, map widgets) in isolated local boundaries with inline fallbacks.
• Unit Testing (frontend/__tests__/ErrorBoundary.test.tsx):
  • Added test suite confirming that child render throws trigger fallback UI without unmounting parent components.

Acceptance Criteria Checklist

• Root boundary renders recoverable UI and resets on route change.
• Local boundaries wrap graph, chart, and map components with inline fallbacks.
• pages/_error.tsx handles server-render failures.
• Caught errors are logged with component stack trace.
• Unit test asserts throwing child renders fallback rather than blank document.
  Closes Frontend: There is no React error boundary anywhere in the frontend, so any render-time throw blanks the page #349