Content index backfill

Daily, fleet-wide and hash-gated: re-indexes every Space's content and every mail copy's attachments where the index lacks a file's current bytes, and retries every file recorded with an indexing gap. Run by the daily schedule as System; a global admin may run it by hand.

Reconnecting…
The connection to the server was interrupted. Trying to restore it…
Trying again…
The connection could not be restored. Reloading the page…
The server was updated. Reloading the page to pick up the latest version.