Restore activeHalfyear and activeMonth nodeinfo

What does this MR do?

It re-adds nodeinfo stats that were removed as part of https://github.com/misskey-dev/misskey/issues/9505 citing performance reasons. My opinion is that the stats are a 'nice to have' on a variety of fediverse reporting sites, and with proxy caching occurring, nodeinfo shouldn't get updated more than a few times per hour.

Wouldn't it have been great to add in a control panel switch to enable/disable these stats?

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