Implement global error handling

[BrayanMQ]

Create centralized error handling system with appropriate UI.

Tasks

1. Create ErrorBoundary component
2. Create error pages (404, 500)
3. Handle API/Supabase errors appropriately
4. Show user-friendly error messages
5. Error logging (optional, for development)
6. Handle network/offline errors

Acceptance Criteria

• Errors are handled appropriately
• Clear messages for user
• Application does not break due to errors
• Custom error pages