Warn user if deletion frequency is likely to hit a rate limit

[codl]

mastodon's is 30 per 30 minutes i think (which is very easy to hit) pleroma's is configurable and 15 per 10 seconds by default. we don't detect pleroma anyway but it's good to know that it's not lower than mastodon twitter's is... not documented? surely there's got to be a limit. the website uses a weirdass graphql api that doesn't return any rate limit headers so that's not helpful