`$ bob run`, `$ bob test`: standardize running the app and running the tests

[joonas-fi]

When after a long time I return back to a project, I don't remember how to run it or there's a special script somewhere to launch it.

Make standard interfaces for these concerns so:

• one doesn't have to remember project-specific settings.
• we can render VSCode's tasks.json (or whatever it was) to offer these commands in GitHub Codespaces and such