Timezone For Point

IANA timezone for a coordinate, on its own.

/public/address-resolve already does this for the normal path. This stays for the case where a point arrives without going through Places — a backfill over shops that predate this field, or a map pin.

Chosen over the timezonefinder package, which does the same thing offline: that pulls 33 MB of bundled boundary shapefiles that then have to be refreshed whenever tzdata changes, permanently, on every build — against roughly $0.005 per signup here.