Geographic country, calling-code and city names: GeoNames, https://www.geonames.org/
Source: https://download.geonames.org/export/dump/countryInfo.txt and cities500.zip
License: Creative Commons Attribution 4.0, https://creativecommons.org/licenses/by/4.0/
Snapshot: 2026-10-21. Cities include settlements over 500 residents or administrative seats; coverage is not exhaustive.
Adaptation: country calling-code normalization and per-country lists of unique city names, sorted for form selection.