fix(ui): design critique overhaul — a11y, honest metrics, i18n repair (critique 2026-08-30)

P0 a11y: keyboard-accessible dropzone (role/tabIndex/Enter-Space), ARIA
combobox + listbox pattern for language selector, role=switch on glossary
toggle, role=status live region on notifications, aria-labels on password
toggles, visible-on-focus close buttons, RTL logical positioning (start-*).

Trust: third-party Memento promo removed from translate page, sidebar and
all 13 locales; fabricated stats (99.9%, Turbo, computed layout-integrity
bars) replaced with real measurements incl. API estimated remaining time;
silent download failure now surfaces an error notification.

Honesty: fake 100-byte file injections removed (format chips are now
informational); cancel-that-doesn't renamed 'Back to start' with hint;
Enterprise contact placeholder replaced with contact@wordly.art.

i18n: t() no longer returns raw keys (empty string + defaultValue support,
~30 dead || fallbacks now work); ~170 new keys EN+FR across new reviews/
teams namespaces, glossaries context tab, translate monitor, settings,
services, pricing, landing, fileUploader; split-key italic titles replace
lastIndexOf() surgery (zh/ja-safe); key-audit script added 0 missing.

Flow: active job persisted across refresh with polling resume (24h TTL);
client-side recent-jobs history with review links; review page linked from
complete state; settings/services added to dashboard nav; Business/
Enterprise regain glossary access (tier gate unified).

Typeset (sober-tool direction): 7.5-9px labels raised to 10-12px, /30
opacity to /45-/55, uppercase tracking reduced, trust footer legible,
country flags removed from language switcher, localized dates.

Cleanup: 5 orphaned translate components, dead site header/footer,
fossil tailwind.config.js, PipelineStepper, duplicate pill+H1 titles,
two-step confirm for cache clear, dead landing footer links.

Verified: next build exit 0, vitest 9/9, eslint 64 errors = HEAD
(no regression, -3 warnings), detector 4 -> 3 findings.

frontend/src/lib/i18n.tsx

@@ -158,8 +158,17 @@ export function I18nProvider({ children }: { children: ReactNode }) {
 
   const t = useCallback(
     (key: string, params?: TranslationParams): string => {
-      const msg = messages[key] ?? enMessages[key] ?? key;
-      return interpolate(msg, params);
+      const msg = messages[key] ?? enMessages[key];
+      if (msg === undefined) {
+        // Missing everywhere: honour an explicit defaultValue, else return ""
+        // so `t(key) || fallback` call sites work and raw keys never reach the UI.
+        return params && "defaultValue" in params
+          ? String(params.defaultValue)
+          : "";
+      }
+      const rest = { ...params };
+      delete rest.defaultValue;
+      return interpolate(msg, rest);
     },
     [messages],
   );