Schedule index file generation

I'd love the ability to schedule the creation of media index files for the off hours.

Mainly this is so that the server isn't bogged down when I'm trying to use it for other things. But also I get buffering issues when there is a second transcoding session running to create the index files.

I agree with this completely.  I want to run indexing overnight when no one is watching anything (and I would like to be able to turn off automatic indexing whenever I add something).

Early 2021 clean-up: implemented (option to schedule periodic scans / maintenance windows for recurring tasks)