Provide prebuilt images for localinstall

Currently localinstall provides a way to build all the Maestro components from scratch. Although it's great for educational purposes, some use-cases might depend only on interacting with Maestro instance (without the infrastructure setup step).

In order to do so (and to make it available quickly), localinstall could use prebuilt images (including cached kernel sources) unless forced to rebuild the whole setup from scratch.

An example of this behavior is available in [lava/pkg/docker-compose](https://gitlab.com/lava/pkg/docker-compose) (see [.env](https://gitlab.com/lava/pkg/docker-compose/-/blob/master/.env#L2)):

- prebuilts are used by default
- user can provide specific image/tag
- [rebuild from scratch can be requested demand](https://gitlab.com/lava/pkg/docker-compose/-/blob/master/Makefile#L6)

Start by locating the localinstall entry point and its current build-from-scratch flow. Compare its behavior with the referenced docker-compose .env and Makefile examples, then define how prebuilts, a user-selected image or tag, and an explicit rebuild request should work. Done means localinstall uses prebuilts by default while retaining an opt-in full rebuild path.

Written by the indexing model from the issue text.