Disable autoloading of Imaginary

[rockstar2020]

Is your feature request related to a problem? Please describe.

Apparently Imaginary is forced to load by default as preview engine for memories.

Describe the solution you'd like

I'd like a way to disable its loading.
This could be managed by adding an environment variable in the docker container.

Describe alternatives you've considered

I have problems with generating thumbnails for my video files in memories and am hoping ffmpeg (without imaginary) could solve this issue.

Additional context

[szaimen]

Hi, if you dont want to use imaginary, simply disable it in the AIO interface.