Supress `DefaultNpmRunner` logs during dev execution and make them available on some endpoint

[vvcaw]

[ClemensElflein]

I guess this is done with today's changes, but maybe we should add an endpoint to the Javalin app during "dev" execution so that we can still have a look at what vite is doing?

E.g. add some route like GET /javalin-vite-logs