fix(ui): wave 2 from critique re-run — AA contrast, unified PageHeader, checkout confirm

Nav: teams/settings/services back out of the nav until product-ready (user
decision); teams page was already half-finished (UUID member display is a
backend limitation).

Payment: explicit confirmation dialog (plan, amount, billing period, Stripe
note) before any redirect; ?plan= URL now pre-opens the dialog instead of
triggering a silent checkout.

Contrast AA sweep (71 replacements): functional micro-labels raised to
>=60-65% opacity and >=10px across sidebar, header, pricing, landing;
decorative all-caps 'interface' label removed.

Design unification: new PageHeader component (accent pill + serif
base/accent title) applied to settings, services, reviews, teams; pricing
header returned to the editorial voice (serif + accent pill); dead
GlossaryCard deleted.

i18n residuals: suggestion chips, 'Standard' provider label, notification
close, model-combobox strings extracted (+broken bg-surface/border-border-
subtle tokens fixed); ~45 new keys EN+FR; 13 dead keys removed; zero
missing keys verified.

Reviews: icon-only row actions now carry visible text; 'Approve all' is
two-step armed-confirm.

Accelerators: Ctrl/Cmd+Enter submits; arrow-key navigation in the language
combobox; recent-jobs history cap 8->20 with per-job download; source=target
config rejected; empty 'Master Quality' badge removed.

Cookie consent: reopenable via footer link, emoji replaced with drawn icon.

Verified: build exit 0, vitest 9/9, eslint 64 errors = previous level,
0 missing i18n keys.

frontend/src/app/dashboard/translate/useTranslationConfig.ts

@@ -233,8 +233,10 @@ export function useTranslationConfig(hasFile: boolean): UseTranslationConfigRetu
   const isConfigValid = useMemo(() => {
     if (!hasFile || !targetLang) return false;
     if (!provider) return false;
+    // Translating a language into itself is always a mistake
+    if (sourceLang !== 'auto' && sourceLang === targetLang) return false;
     return true;
-  }, [hasFile, targetLang, provider]);
+  }, [hasFile, targetLang, provider, sourceLang]);
 
   const getConfig = useCallback((): TranslationConfig => ({
     sourceLang,