serve pairs from per-city index (numbeo rankings): 361 cities, up to 10/country, all 92 capitals; myanmar->yangon

expand numbeo cache to all-capital pairs via per-city index

serve cross-country comparisons from an offline numbeo cache

switch numbeo scraper to curl_cffi with chrome tls impersonation

harden numbeo fetch with browser headers, cookie priming and retry

split dense README into docs/ (architecture, testing, deployment)