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/personas-panel.tsx

@@ -124,7 +124,7 @@ export function PersonasPanel({ noteTitle, noteContent }: PersonasPanelProps) {
         body: JSON.stringify({ content: noteContent, title: noteTitle, personaId }),
       })
       const data = await res.json()
-      if (!res.ok) throw new Error(data.error || t('common.error'))
+      if (!res.ok) throw new Error(data.errorKey ? t(data.errorKey) : (data.error || t('common.error')))
       setResults(prev => new Map(prev).set(personaId, data))
       setExpanded(personaId)
     } catch {