Add the control plane UI

[peterschmidt85]

Currently, dstack only offers CLI and API to manage projects, users, runs, etc. Moreover, even the CLI doesn't allow to manage users and projects. If dstack is used by an organization (which is the main use case), teams need a convenient UI to manage projects, users, runs, etc.

Currently, such a UI is only included in dstack Sky and the open-source users of dstack cannot use similar features. For organizations, this is a blocker to adopt the open-source version.

The source code of the control plane UI should be moved to this repo and the build/release workflow should be updated accordingly to bundle the static files into the release.

Note, if dstack is launched from the sources (or pip install from GitHub), it should work as now - redirect to the Swagger UI.

[r4victor]

Closed by #1524