formatDate special-cased only French, so Danish users saw US
mm/dd/yyyy; formatDateTime mixed a manual French format with
toLocaleString() (OS-locale dependent) for everyone else. Both now use
Intl.DateTimeFormat with a fixed app-language -> BCP-47 map (en-US,
fr-FR, da-DK — same mapping as useSpeech), 2-digit day/month so output
stays deterministic per language: en 03/15/2026, fr 15/03/2026,
da 15.03.2026. Adds a Danish format test.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
David