[talk-au] Duplicate node finder

[Grant Slater]

> But zoom levels six and lower are still showing marks that have been
> removed for at least a day. They must be updated at some lower
> frequency, which is understandable - I'm guessing there is some
> clumping of many marks into one, or it would take forever to display
> at these zooms.
>

The lower zooms have now been updated.

z 0 - 6 are filesystem cached and currently require a manual purge.

/ Grant