feat: add error boundaries to prevent app crashes

[kennethkabogo]

Description

This PR implements React Error Boundaries across the client application to prevent catastrophic app crashes (white screens) and provide a graceful fallback UI when errors occur.

Key changes:

• Root Level: Wrapped the entire app in app/_layout.tsx to catch unhandled errors and show a full-screen fallback.
• Feature Level: Added boundaries to critical features like ChatManager and DataPreloader to isolate failures (e.g., if chat fails, the wallet might still work).
• Components: Created reusable ErrorBoundary and ErrorFallback components using react-error-boundary.
• UX: The fallback UI includes a "Try Again" button to allow users to recover from transient errors without reloading the entire app.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• [✔️ ] New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Release (version bump)

Release

Is this a release? No

Testing

• Unit Tests: Added apps/client/tests/unit/ErrorBoundary.test.tsx to verify:
  • Error catching at different levels (root, feature, component).
  • Correct rendering of the fallback UI.
  • "Try Again" reset functionality.
  • Dev-mode error details.
• Manual Verification: Verified that throwing errors in wrapped components triggers the fallback UI instead of crashing the app.

Checklist

• [ ✔️] My code follows the project's style guidelines
• [✔️ ] I have performed a self-review of my own code
• [ ✔️] I have commented my code, particularly in hard-to-understand areas
• [ ✔️] My changes generate no new warnings or errors
• [ ✔️] I have added tests that prove my fix is effective or that my feature works
• [ ✔️] New and existing tests pass locally with my changes
• [ ✔️] If releasing, I have verified the version number is correct and follows semantic versioning