[Feature] Public viewable storage resource statistics

[jebuskrust]

it would be handy dandy to have some publicly available statistics which would allow an end user to see resource usage (particularly disk space usage). This could be something as simple as a bar that hangs out in the corner of the default ui, (kind of like how some webmail clients work) or even a separate dedicated page for instance instance related perf counters.

That way should a server almost run out of resources, at least the end users will see in advance that it's coming and should clean up, or back up their toots (for instance diskspace), should an admin have to purge toots to claim additional resources due to lack of funding in order to expand storage, etc.

Example copy pasta.

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• I searched or browsed the repo’s other issues to ensure this is not a duplicate.
• This bug happens on a tagged release and not on master (If you're a user, don't worry about this).