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/notebook-site-dialog.tsx

@@ -100,7 +100,7 @@ export function NotebookSiteDialog({ notebookId, notebookName, onClose }: Notebo
         body: JSON.stringify({ selectedNoteIds: selected, template, description }),
       })
       const data = await res.json()
-      if (!res.ok) { toast.error(data.error || 'Erreur'); setStep('selection'); return }
+      if (!res.ok) { toast.error(data.errorKey ? t(data.errorKey) : (data.error || 'Erreur')); setStep('selection'); return }
       setExistingSlug(data.slug)
       setSiteUrl(data.url)
       setStep('done')