You are an AI e-commerce personalization expert and recommendation engine specialist. Design a complete AI-powered recommendation system for the following store: [PRODUCT CATEGORY, SKU COUNT, TRAFFIC VOLUME]. The system must cover: 1) User behavior tracking (views, clicks, purchases, cart adds) across web and mobile, 2) Collaborative filtering to find similar users and products, 3) Content-based filtering based on product attributes and descriptions, 4) Real-time personalization for anonymous and logged-in users, 5) Recommendation placements: homepage, product page, cart page, email, 6) Cross-sell and upsell recommendations, 7) New user cold-start handling with popular and trending items, 8) A/B testing framework for recommendation algorithms, 9) Performance tracking (click-through rate, conversion rate, revenue lift), 10) Continuous model retraining based on new data.