i18n: fix missing keys and translate all non-admin frontend strings

- Add 12 missing i18n keys (t() was returning the literal key string) to
  all 13 locales: dashboard.topbar.premiumAccess,
  dashboard.translate.complete.toastOkDesc,
  dashboard.translate.progress.{connectionLost,processingFallback},
  glossaries.card.{term,created}, glossaries.termEditor.{addTerm,maxReached},
  login.google.{connecting,errorFailed,errorGeneric}, login.orContinueWith
- Add 6 FR-drift keys (landing.pricing.{free,enterprise}.{name,desc,cta})
- Add ~120 new i18n keys covering site header/footer, file-uploader,
  checkout success, dashboard pages, translate page, provider selector
  themes, language selector, translation complete, api-keys, services,
  settings, pricing (~1800 new key/locale pairs)
- Wrap hardcoded French/English in components with t() calls
- Convert LLM_THEMES/CLASSIC_THEMES/FALLBACK_PROVIDERS maps from
  hardcoded constants to t()-driven factories
- Admin pages intentionally left untouched per request

Files: 15 components/pages + src/lib/i18n.tsx
Typecheck: passes (tsc --noEmit exit 0)

frontend/src/app/dashboard/services/page.tsx

@@ -5,8 +5,8 @@ import { Zap, CheckCircle2, Lock, Loader2, Globe, Brain } from 'lucide-react';
 import { API_BASE } from '@/lib/config';
 import { useI18n } from '@/lib/i18n';
 
-const FALLBACK_PROVIDERS = [
-  { id: "google", label: "Google Traduction", description: "Traduction rapide, 130+ langues", mode: "classic" as const },
+const FALLBACK_PROVIDERS_FACTORY = (t: (k: string) => string) => [
+  { id: "google", label: t('services.fallback.google.label'), description: t('services.fallback.google.desc'), mode: "classic" as const },
 ];
 
 interface AvailableProvider {
@@ -19,6 +19,7 @@ interface AvailableProvider {
 
 export default function TranslationServicesPage() {
   const { t } = useI18n();
+  const FALLBACK_PROVIDERS = FALLBACK_PROVIDERS_FACTORY(t);
   const [providers, setProviders] = useState<AvailableProvider[]>([]);
   const [isLoading, setIsLoading] = useState(true);
 
@@ -43,7 +44,7 @@ export default function TranslationServicesPage() {
       }
     };
     fetchProviders();
-  }, []);
+  }, [FALLBACK_PROVIDERS]);
 
   const classicProviders = providers.filter((p) => p.mode === "classic");
   const llmProviders = providers.filter((p) => p.mode === "llm");