Show ages on the AS and prefix pages in words (closes #163)

The Age column printed Go's duration format for every plural age, such
as "5m0s ago" or "360h0m0s ago".

The templates now register humanize.Time from go-humanize, which the
server already uses, as the timeSince function, and the hand-written
function is gone. Ages read "5 minutes ago", "3 hours ago" or "2 weeks
ago". An age under a minute reads "now" or in seconds instead of "just
now". An age over a month reads in months or years instead of a date.

Model: opus-5-5

TODO.md

@@ -33,6 +33,10 @@ tested.
 
 # Completed Steps
 
+- 2026-10-27: the Age column on the AS and prefix pages reads in words, such as
+  "5 minutes ago" or "2 weeks ago", instead of Go durations such as "360h0m0s
+  ago". An age under a minute reads in seconds, and one over a month in months
+  or years instead of a date (closes #163)
 - 2026-10-26: a write to a stored AS, peering or peer keeps the earlier of the
   two first-seen times and the later of the two last-seen times. An old update
   from a collector catching up on a backlog no longer moves last seen back