callDuckDuckGoHtml hardcoded kl=us-en and never read parsedQuery.lang, so
the shared lang: directive was silently discarded — unlike the Perplexity
and SearXNG providers, which map it. Distinct locales collapsed to the same
request.
Added localeToKl mapping the parsed language-region locale onto DDG's
region-language kl code (swapping components, gb->uk alias), falling back to
us-en for language-only, malformed, or absent locales.
Fixes#7110
roboomp
9cd42dd8f9