Do signature checking in the background

[jb55]

We should have a work queue to process things in the background, like preloading PFPs, etc. We shouldn't see anything popping in.

[jb55]

This is done for PFPs now but we'll probably need it for processing signatures since that seems to be blocking the thread when scrolling on slower devices

[jb55]

We need to do a bunch of processing in the background when we received a post. I've noticed the parsing content for mentions, etc can be somewhat time consuming as well. so perhaps this call all be done right away in a work queue.

[jb55]

This is fixed by nostrdb +

• https://github.com/damus-io/damus/issues/2041