Summary: Added "纳米AI" product and related content.

Why It Matters: This shows a new focus on AI products.

What Changed:

• Removed many product listings and links from the main navigation.
• Added "纳米AI" to the main navigation.
• Added a new section for "纳米AI" with download links.
• Added new sections for "360智脑大模型" and "AI办公" products.
• Removed sections for "SaaS 服务推荐", "安全热点关注", "360安全软件", "360商城", "新闻动态", "安全资讯", "社区热帖", and "电脑安全".
• Updated the "360新闻资讯" section with new categories and content.
• Updated the "360安全卫士" section with a new AI focus.
• Removed many specific product links from the footer.
• Added "登录" and "注册" links to the top right.
• Added a "个人中心" and "退出" option.
• Added a trending topics list.