idea: stats page showing an overview of the shards

[db48x]

I'd like a way to see at a glance which shards ought to be active (because they don't have a good availability level) and which can just be in maintenance mode. Perhaps a grid of squares, with each square colored according to the percentage of files with >=3 backups? Small square bar-graphs showing the change over time?

It should also have annotations to show which shards are currently active, to identify shards that have been brought up to spec, so that we can change them to maintenance mode.