Mirror of wowcheckout e0c349a. Same bug would bite xmrcheckout after any api container rebuild — nginx caches IP at startup and never re-resolves, so a rebuild that gives the api container a new IP leaves nginx 502'ing until manually restarted. Use 'resolver 127.0.0.11 valid=10s' + variable-based proxy_pass so nginx re-resolves every ~10s via Docker's internal DNS.
