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/notebook-slides/route.ts

@@ -0,0 +1,62 @@
+import { NextRequest, NextResponse } from 'next/server'
+import { auth } from '@/auth'
+import { withAiQuota, handleQuotaHttpError } from '@/lib/ai-quota'
+import { hasUserAiConsent, aiConsentForbiddenResponse } from '@/lib/consent/server-consent'
+import { generateSlideDeck } from '@/lib/ai/services/slide-deck-generator.service'
+
+export async function POST(request: NextRequest) {
+  try {
+    const session = await auth()
+    if (!session?.user?.id) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
+    }
+
+    if (!(await hasUserAiConsent())) {
+      return aiConsentForbiddenResponse()
+    }
+    const userId = session.user.id
+
+    const body = await request.json()
+    const { notebookId, theme, purpose, audience, slideCount, language } = body
+
+    if (!notebookId || typeof notebookId !== 'string') {
+      return NextResponse.json({ error: 'notebookId is required' }, { status: 400 })
+    }
+
+    const intent =
+      purpose || audience || slideCount
+        ? {
+            purpose: purpose || 'auto',
+            audience: audience || 'auto',
+            slideCount: typeof slideCount === 'number' ? slideCount : undefined,
+            template: 'auto' as const,
+          }
+        : null
+
+    const result = await withAiQuota(
+      userId,
+      'slide_generate',
+      () =>
+        generateSlideDeck({
+          userId,
+          sourceNotebookId: notebookId,
+          theme: theme && theme !== 'auto' ? theme : null,
+          lang: language === 'en' ? 'en' : 'fr',
+          intent,
+        }),
+      { lane: 'chat' },
+    )
+
+    if (!result.success) {
+      return NextResponse.json({ error: result.error || 'Failed to generate slides' }, { status: 500 })
+    }
+
+    return NextResponse.json(result)
+  } catch (error: unknown) {
+    const quotaResp = handleQuotaHttpError(error)
+    if (quotaResp) return quotaResp
+    console.error('[NotebookSlides] Error:', error)
+    const message = error instanceof Error ? error.message : 'Failed to generate slides'
+    return NextResponse.json({ error: message }, { status: 500 })
+  }
+}