Create default glance.yml file during first start as fallback

### Description

It would be great if the glance application would come with a `glance.yml` initially or would create the default `glance.yml` automatically during first startup.
This would enable users to have an already running application during first startup and can manually adjust their `glance.yml` file later how they desire.

Start by tracing the application's first-startup path and the point where glance.yml is loaded. Determine how a default glance.yml can be available before normal configuration loading; done means a fresh launch works without a user-created file and the resulting configuration can be edited later.

Written by the indexing model from the issue text.