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/app/api/ai/suggest-charts/route.ts

@@ -5,7 +5,7 @@ import { getSystemConfig } from '@/lib/config'
 import { prisma } from '@/lib/prisma'
 import { auth } from '@/auth'
 import { reserveUsageOrThrow, QuotaExceededError, QuotaServiceUnavailableError } from '@/lib/entitlements'
-import { hasUserAiConsent } from '@/lib/consent/server-consent'
+import { hasUserAiConsent, aiConsentForbiddenResponse } from '@/lib/consent/server-consent'
 
 export const maxDuration = 30
 
@@ -41,10 +41,7 @@ export async function POST(req: Request) {
   }
 
   if (!(await hasUserAiConsent())) {
-    return new Response(JSON.stringify({ error: 'ai_consent_required' }), {
-      status: 403,
-      headers: { 'Content-Type': 'application/json' },
-    })
+    return aiConsentForbiddenResponse()
   }
   const userId = session.user.id