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/describe-image/route.ts

@@ -2,7 +2,7 @@ import { NextRequest, NextResponse } from 'next/server'
 import { auth } from '@/auth'
 import { getAISettings } from '@/app/actions/ai-settings'
 import { describeImages } from '@/lib/ai/services/image-description.service'
-import { hasUserAiConsent } from '@/lib/consent/server-consent'
+import { hasUserAiConsent, aiConsentForbiddenResponse } from '@/lib/consent/server-consent'
 import { withAiQuota, handleQuotaHttpError } from '@/lib/ai-quota'
 
 export async function POST(req: NextRequest) {
@@ -13,7 +13,7 @@ export async function POST(req: NextRequest) {
     }
 
     if (!(await hasUserAiConsent())) {
-      return NextResponse.json({ error: 'ai_consent_required' }, { status: 403 })
+      return aiConsentForbiddenResponse()
     }
 
     const userSettings = await getAISettings(session.user.id)