Actually run eslint ;)

[dokterbob]

It turned out that:

• eslint (and tsc) weren't being run for all projects in the workspace, it was only being run for frontend.
• Moreover, due to a version mismatch between eslint and eslint-typescript, eslint wasn't actually running on frontend either.
• tsc wasn't configured to run on lint for react-client

This patch resolves this and fixes some minor linting issues which came up.

Note that I ran into issues with tsc validation of copilot -- while this problem didn't occur for react-client. The solutions is probably to use composite in the typescript config's. That's basically workspace support for typescript and should be a separate issue.