fix: replace raw ai_consent_required code with translatable message and consent prompt

- Centralize AI consent 403 responses in server-consent helpers
- Return human-readable message + code + i18n errorKey from all AI APIs
- Update dashboard and AI clients to detect code/errorKey and translate
- Add consent.ai.requiredToast i18n keys (fr/en)

memento-note/components/wizard/ai-notebook-wizard.tsx

@@ -100,7 +100,7 @@ export function AiNotebookWizard({ onClose, onComplete }: { onClose: () => void;
         } else if (data.errorKey === 'ai.quotaExceeded') {
           toast.error(t('ai.quotaExceeded') || 'Quota IA dépassé')
         } else {
-          toast.error(data.error || 'Erreur')
+          toast.error(data.errorKey ? t(data.errorKey) : (data.error || 'Erreur'))
         }
         setLoading(false)
         return