Audit follow-up to the Spanish-locale commit: `CustomerDetailPage` had
a hardcoded `<option>` list for the customer's preferred-language
selector — 5 entries (en/de/nl/pt/ru) that were missing both fr (an
existing gap) and es (the new one). Every other language selector in
the frontend (the navbar `LanguageSelector`, the `GeneralTab` default-
language dropdown, the `EmailConfigPage` per-language tabs) already
reads from the shared `SUPPORTED_LANGUAGES` constant, so adding es
there was enough for those. This one had drifted.
Now mapped from `SUPPORTED_LANGUAGES` so future locales only need to
touch one place.
Paul Nothaft
51890e1aa5