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/agents/agent-card.tsx

@@ -128,7 +128,7 @@ export function AgentCard({ agent, onEdit, onRefresh, onToggle }: AgentCardProps
             if (pollRef.current) clearInterval(pollRef.current)
             pollRef.current = null
             setIsRunning(false)
-            toast.error(t('agents.toasts.runError', { error: data.error || t('agents.toasts.runFailed') }), { 
+            toast.error(t('agents.toasts.runError', { error: data.errorKey ? t(data.errorKey) : (data.error || t('agents.toasts.runFailed')) }), { 
               id: toastId,
               description: '' // Clear the loading description
             })