feat(ai): localize AI features

keep-notes/app/api/ai/notebook-summary/route.ts

@@ -17,7 +17,7 @@ export async function POST(request: NextRequest) {
     }
 
     const body = await request.json()
-    const { notebookId } = body
+    const { notebookId, language = 'en' } = body
 
     if (!notebookId || typeof notebookId !== 'string') {
       return NextResponse.json(
@@ -45,7 +45,8 @@ export async function POST(request: NextRequest) {
     // Generate summary
     const summary = await notebookSummaryService.generateSummary(
       notebookId,
-      session.user.id
+      session.user.id,
+      language
     )
 
     if (!summary) {