Rename error-page.tsx to ErrorPage.tsx (#1497)

## Summary
- Renamed the route error component module from kebab-case
`error-page.tsx` to PascalCase `ErrorPage.tsx`, matching the rest of
`src/`.
- Updated the `main.tsx` import accordingly.

Closes #1492.

## Test plan
- [x] `pnpm lint` (ESLint / Prettier hooks pass on CI)
- [x] Open a route that renders the error boundary and confirm the page
still loads.

Made with [Cursor](https://cursor.com)

Author: dcblundell

src/error-page.tsx src/ErrorPage.tsxsrc/error-page.tsx renamed to src/ErrorPage.tsx

@@ -10,7 +10,7 @@ import { FocusStyleManager, OverlaysProvider } from '@blueprintjs/core';
 import './index.scss';
 import { HelmetProvider } from 'react-helmet-async';
 import { RouterProvider } from 'react-router';
-import ErrorPage from './error-page';
+import ErrorPage from './ErrorPage';
 import Layout from './components/Layout';
 import getServerConfig from './functions/getServerConfig';
 import { SocketProvider } from './libs/SocketProvider';