fix: AI 업셀링 생성을 별도 스레드로 분리 — 키오스크 적립 응답 블로킹 방지

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app.py

@@ -2384,11 +2384,14 @@ def api_kiosk_claim():
         except Exception as alimtalk_err:
             logging.warning(f"[알림톡] 발송 예외 (적립은 완료): {alimtalk_err}")
 
-        # AI 업셀링 추천 생성 (fire-and-forget)
-        try:
-            _generate_upsell_recommendation(user_id, transaction_id, sale_items, user_name)
-        except Exception as rec_err:
-            logging.warning(f"[AI추천] 생성 예외 (적립은 완료): {rec_err}")
+        # AI 업셀링 추천 생성 (별도 스레드 — 적립 응답 블로킹 방지)
+        import threading
+        def _bg_upsell():
+            try:
+                _generate_upsell_recommendation(user_id, transaction_id, sale_items, user_name)
+            except Exception as rec_err:
+                logging.warning(f"[AI추천] 생성 예외 (적립은 완료): {rec_err}")
+        threading.Thread(target=_bg_upsell, daemon=True).start()
 
         return jsonify({
             'success': True,