Feature: Manual deletion

[Bakeneko]

I'm still running in dry-run for two reasons:

1. I'm almost done searching the sweet spot with tag protection and filters (but considering having a go at Any plans for audience / critic rating filtering? #234).
2. Despite my 35TB library deletions are infrequent enough that I prefer to maintain control of the final "purge" process (I would still have to delete my download/cross-seed hardlinks orphans anyway).

The main drawback of staying in dry-run is that users don't receive notifications regarding seerr requests, but I can live with that.

I took a quick look at the code and I have a proposal.

Auto vs Manual deletion

Add a boolean config to toggle auto/manual deletion and check it before calling cleanupMedia().
So the whole cleanup job flow would ran, except for the purge.

Any thoughts? Or should I just disable dry-run, close my eyes and let go 😅.