The dashboard now speaks seven languages but every failure path still showed
the API's raw English text ("insufficient balance", "current password is
incorrect"), which is the most frequent and least forgiving part of the UI to
leave untranslated.
Rather than teach the API about locales, it keeps answering in one language
and hands the client something to translate: `detail` becomes
{code, message, params}, where message stays English for non-dashboard
consumers (curl, tests) and code maps onto `error.<code>` in i18n.js. An
unknown code falls back to message, so a client older or newer than the server
degrades to English instead of a blank toast.
Domain exceptions (BetError, WithdrawalError) subclass the new ApiError and
carry the code from where the failure actually happens; str(exc) is still the
English message, so existing tests keep matching on it. Interpolated values
travel in params rather than baked into the English sentence — amounts as
*_sats, from which the frontend derives a *_plm sibling, so each language can
place them wherever its grammar wants.
admin.js reads detail.message defensively: the admin endpoints still return a
bare string, but the shared auth dependencies now return the structured form.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Argon2 password hashing, JWT session issuing/verification
(auth/security.py), register/login routes, the bearer-token
get_current_user dependency, and GET /users/me for address + balance.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>