[Bug] 404 page has black background with no navigation or app styling

## Description
Navigating to an unknown route shows a bare black 404 page with no navigation or styling.

## Steps to Reproduce
1. Navigate to https://wallet.testring.org/wallet

## Expected Behavior
404 page is styled consistently with the app and includes a home link.

## Actual Behavior
Black page with only "404 | This page could not be found." — no way to navigate back.

## Severity
Medium