[FEAT] Option to start calibre webserver only

[Skeeve]

Is this a new feature request?

• I have searched the existing issues

Wanted change

I usually do not want to always run the gui. Is there an option to initially only start the webserver?

Reason for change

While we are at it: is there a way to stop and later start the GUI? I only need the GUI when I insert new books or do maintenance on my library. Otherwise the webserver is sufficient.

I also want to use rsync to backup my calibre library to my NAS and calibre gui shouldn't run during that period as it could change the data while it is being accessed for backups.

My idea was, after stopping the gui, the rsync kicks in.

Proposed code change

no idea

[github-actions]

Thanks for opening your first issue here! Be sure to follow the relevant issue templates, or risk having this issue marked as invalid.